Semiconductor memory, memory device, and memory card

ABSTRACT

A semiconductor memory (1), having a plurality of memory blocks (2 and 3) provided with a plurality of memory cells, a data input/output buffer (7), and first control means (11) for controlling the rewriting and reading of data for the memory cells is provided with first storage means (30) for designating defective memory blocks and detection means (32) for detecting an access to a defective memory block designated by the first storage means in accordance with an address signal. When the detection means detects an access to a defective memory, the first control means inhibits the data rewrite operation for an instruction for a data rewrite operation and inhibits the output of data from the input/output buffer for the data read operation. The inhibiting function makes it possible to provide a memory device having compatibility with a non-defective semiconductor memory only by combining semiconductor memories having irremediable defects without fixing the levels of specific address input terminals so as to keep the defective memory blocks non-selective.

BACKGROUND OF THE INVENTION

1. Technical Field to which the Invention Belongs

The present invention relates to an art making it possible to achievecomplete compatibility with a non-defective semiconductor memory bycombining semiconductor memories having irremediable local defects,particularly to an art for constituting a memory device or a memory cardby combining a plurality of flash memories having irremediable defectswhich can be apparently ignored.

2. Technical Background of the Invention

When some of the memory cells in a semiconductor memory are defective,it is possible to repair the semiconductor memory by replacing thedefective memory cells with redundant memory cells. However, when amalfunctioning portion of a semiconductor memory exceeds a remediablerange, the semiconductor memory is regarded as defective. Asemiconductor memory having no malfunctioning portion or whosemalfunctioning portion is in a remediable range is referred to as acomplete composite conforming circuit. The defective product can be usedas an operable product by removing defective portions from the memoryand decreasing the entire memory capacity of the memory to 1/2 or 1/4.This locally operable product is a partial product. Partial products canbe used by mutually combining partial products in which the operableportion of one partial product compensates the inoperable portion of theother product. For example, in the case of a low-order partial product,in which the high-order half of the memory area is defective, and ahigh-order partial product, in which the low-order half of the memoryarea is defective, it is possible to use these partial products incombination by fixing the address input terminal of an address bitprovided to select the high order or low order portion of the memoryarea to the selection level of a low-order side memory area at theoutside, in the case of the low-order partial product, and fixing theaddress input terminal of an address bit provided to select the highorder or low order portion of the memory area at the outside in the caseof a high-order partial product.

When the data input/output terminals of the high-order partial productand low-order partial product are connected to each other in common atthe outside to use the partial products instead of a non-defectiveproduct, chip selection must be performed for each partial product byusing different chip selection signals. Therefore, to use a partialproduct for a semiconductor memory in a memory card, it is necessary toincrease the number of chip selection signals compared to the case wherea non-defective product is used, and moreover, it is necessary to use adecoder having different logic for chip selection when using a partialproduct in comparison to that a non-defective product.

Moreover, each defective portion of a plurality of partial products mayhave a difference depending on -the fabrication process. When combininga plurality of partial products in which defective-portion tail addressregions are complementary instead of using a non-defective product, ifthe partial products having different defective portions are biased inquantity, a larger portion of the partial products are left unused.

Furthermore, in the case of a nonvolatile semiconductor memory, such asa flash memory, rewriting of information is performed by bringing thememory cells into an erasing state and then data write is performed.Also, a verify operation is necessary for the erase and writeoperations. In the case of a semiconductor memory, such as a flashmemory, erase, erase verify, write, and write verify operations arecontrolled inside the memory so that data can be written even on thesystem (on-board state). The state in which a rewrite operation isperformed inside is reported to an access body, such as amicroprocessor, in accordance with, for example, a ready/busy signal.When a failure occurs in the erase operation or write operation due todeterioration of the characteristics of a memory cell, an erase state orwrite state necessary for the memory cell cannot be obtained even if theerase and erase verify operations and write and write verify operationsare repeated many times and the internal rewrite control operation isabnormally ended.

It is an object of the present invention to provide a semiconductormemory which directly applicable to a memory device and a memory card byusing a plurality of partial products instead of a non-defective productor complete composite conforming circuit.

It is another object of the present invention to provide a semiconductormemory which is capable of preventing a contradiction of the internalstates from occurring between a partial product in which the operationof its defective portion is designated by an access from an externalunit and another partial product substituted for the former partialproduct, and, moreover, to provide a memory device using the memory.

It is still another object of the present invention to provide asemiconductor memory which is capable of changing the addressarrangement of an operable portion separated from a defective portionirrespective of built-in address decoding logic, and, moreover, toprovide a memory device using the memory.

It is still another object of the present invention to provide a memorycard which is capable of using an address decoding logic for chipselection for a semiconductor memory in common with a case where acomplete composite conforming circuit is used even when a partialproduct is used.

The above and other objects and novel features of the present inventionwill become more apparent from the description provided in thisspecification and the accompanying drawings.

SUMMARY OF THE INVENTION

Semiconductor memories (1, 1C) of the present invention include aplurality of memory blocks (2, 3 or 2Y, 3Y) constituted by a pluralityof memory cells, a data input/output buffer (7) to which data to bewritten in the memory blocks is supplied and which outputs the data readout of the memory blocks to an external unit, and first control meansfor controlling the rewriting of data into and the reading of data fromthe memory cells. The first control means is denoted by symbol 11 inFIG. 1 and by symbols 43Y, 45, and 46Y in FIG. 31. The semiconductormemories are provided with first storage means (30, 47) for designatingdefective memory blocks included in the above memory blocks anddetection means (32, 48Y) for detecting the access to the defectivememory blocks designated by the first storage means in accordance withan address signal. In this case, when the detection means detects anaccess to the defective memory blocks, the control means inhibits a datarewrite operation in the case of a data rewrite operation and inhibits adata output operation of the data input/output buffer in the case of adata read operation.

Moreover, semiconductor memories (1, 1B, or 1C) according to anotheraspect of the present invention include a plurality of memory blocks (2,3 or 2Y, 3Y) constituted by a plurality of electrically erasable memorycells, a data input/output buffer (7) to which data to be written in thememory blocks is supplied from an external unit and which outputs dataread out of the memory blocks to an external unit, and first controlmeans for controlling the writing of data into and the reading of datafrom the memory cells. The first control means is denoted by symbol 11in FIG. 1, and by symbols 43, 44, 45, and 46 in FIG. 15 and by symbols43Y, 45, and 46 in FIG. 31. The semiconductor memories are provided withfirst storage means (30, 47) for designating defective memory blocksincluded in the above memory blocks and detection means (32, 48, 48Y)for detecting an access to the defective memory blocks designated by thefirst storage means in accordance with an address signal. The controlmeans is set to a status (MR/B) representing the completion of the datarewrite operation in the case of a data rewrite operation when thedetection means detects an access to the defective memory blocks so thatthe status can be output to an external unit irrespective of thecompletion of the data rewrite operation, and the control means is setto inhibit a data output operation of the data input/output buffer inthe case of a data read operation.

A semiconductor memory according to still another aspect of the presentinvention includes a plurality of memory blocks (72, 73) constituted bya plurality of memory cells, data input/output buffers (77L, 77U) towhich data to be written in the memory blocks is supplied from anexternal unit and which outputs data read out of the memory blocks to anexternal unit, and first control means for controlling the writing ofdata into and the reading of data from the memory cells, the firstcontrol means having first storage means (100) for designating defectivememory blocks included in the above memory blocks. In this case, thecontrol means inhibits a data rewrite operation for the defective memoryblocks designated by the first storage means in the case of a datarewrite operation and inhibits the data output operation of the datainput/output buffer in the case of a data read operation.

It is possible to use the least significant bit (A0) or the mostsignificant bit (A20) of an address signal for the address informationfor designating a defective memory block.

To realize an arrangement of the addresses of defective memory blocks ona semiconductor memory, it is possible to provide logic means (104) forselectively inverting the inputs so that the inputs can be output andsecond storage means (34) for storing control information fordetermining the propriety of the input inverting operation by the logicmeans for a path for supplying address information to the detectionmeans in order to detect an access to the defective memory blocksdesignated by the first storage means.

By using the above semiconductor memories as partial products, it ispossible to realize a compatible product having the same memory capacityas that of a semiconductor memory of a complete composite conformingcircuit using a memory device (40) which includes the semiconductormemories (1-L, 1-U) having the relation that one semiconductor memory issubstituted for the defective memory block of the other semiconductormemory and vice versa, and in which an external terminal having the samefunction is connected between the semiconductor memories in common.

A memory card (50) using the memory devices is constituted by mounting aplurality of memory devices on a card substrate. Each memory device isprovided with an external-data input/output terminal, a chip selectionterminal and an address input terminal, all serving as the aboveexternal terminals, in which the chip selection terminal is connected tochip-selection signal wirings different from each other on the cardsubstrate and external address input terminals of the memory devices areconnected to address signal wirings of the card substrate in common, forevery memory device in which the external-data input/output terminal isconnected to the data wiring on the card substrate in common.

The memory card is provided with a card controller (52), having one endwhich is interfaced with the outside of the card substrate and anotherend which is connected to the data wiring, chip selection signal wiringsand address signal wirings, and the card controller can be constitutedby including decoding means (54) for decoding part of the addressinformation supplied from an external unit to generate the chipselection signal.

According to the above-described means, when a memory block selected inaccordance with the address information supplied from an external unitcoincides with a memory block (defective memory block in a partialproduct) designated by the first storage means, a data rewrite operationis inhibited by the first control means in the case of a data rewriteoperation, and a data output operation of the data input/output bufferis inhibited by the first control means in the case of a data readoperation. By means of another aspect, when access to a defective memoryblock is detected, a status representing the completion of the datarewrite operation is set up so that it can be output to an external unitby the first control means irrespective of the completion of theoperation in the case of a data rewrite operation, and a data outputoperation of the data input/output buffer is inhibited by the firstcontrol means in the case of a data read operation.

The inhibiting of a semiconductor memory used as a partial product makesit possible to use a partial product without requiring the processing offixing a specific address for designating a memory block outside thesemiconductor memory on a system. For example, when the abovesemiconductor memory is provided with two memory blocks, by combining asemiconductor memory (1-U) used as a high-order partial product and asemiconductor memory (1-L) used as a low-order partial product to form amemory device (40) by connecting its external terminals in common, thememory device (40) achieves the compatibility of a semiconductor memoryhaving a complete composite conforming circuit from the viewpoint ofexternal terminal specification or utilization mode.

In the case of a semiconductor memory, such as a flash memory, whichindependently performs the processing of responding to a commandsupplied from an external unit, even if an instruction to execute theinformation rewrite operation is given from an external unit to adefective memory block in a partial product, the information rewriteoperation of the memory block is inhibited or a status representing thecompletion of the data rewrite operation is set up so that it can beoutput to the external unit irrespective of the completion of theoperation as described above. Therefore, when an instruction to executethe operation of a defective portion of a partial product is given by anaccess from an external unit, it is possible to prevent contradictionfrom occurring in the internal state between the partial product andanother partial product substituted for the defective portion of theformer partial product.

It is considered that defective portions of a plurality of partialproducts are biased depending on the fabrication process. By using thelogic means for selectively logic-inverting address information providedto select a memory block in accordance with a value preset in the secondstorage means, it is possible to optionally change the arrangement ofmemory blocks apparently operable with respect to an address signalsupplied from an external unit depending on the type of settinginformation provided by the second storage means even if partialproducts whose defective portions are different from each other arebiased in quantity. Thereby, when substituting partial products whoseoperational regions are complementary for a non-defective product bycombining them, it is possible to prevent defective partial products ofone defect type more than the other defect type in quantity to be leftunused.

For example, when a flash memory is used as a semiconductor memory andthe semiconductor memory is provided with two memory blocks, it ispossible to mount a semiconductor memory used as a high-order partialproduct and a semiconductor memory used as a low-order partial producton a memory card using the partial product of the semiconductor memoryprovided with two memory blocks by substituting the high-order andlow-order partial products for a complete composite conforming circuitand connecting the external terminals thereof in common on a wiringboard. Because the processing for the defective portion of asemiconductor memory used as a partial product is realized in thesemiconductor memory, the processing for fixing a specific addressterminal of t;he semiconductor memory is not required at all. Even if asemiconductor memory used in a memory card is a partial product, it ispossible to use in common the wiring of a mounting board and the logicof a card controller, particularly the logic of a chip selecting decoderof a semiconductor memory.

Thus, the present invention makes it possible to realize a goodcompatibility between a memory device or memory card using a partialproduct and a device or memory card using a complete compositeconforming circuit. It is possible to directly employ a partial productof a semiconductor memory for a memory device or memory card in place ofa complete composite conforming circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a flash memory representing a firstembodiment of the present invention;

FIG. 2 is a logic circuit diagram of the address input buffer of FIG. 1;

FIGS. 3(A) and 3(B) are diagrams of an embodiment of a memory deviceusing the partial product of the flash memory described with referenceto FIG. 1;

FIG. 4 is a logic circuit diagram of a circuit for generating aready/busy signal and a read/busy status af a partial productconstituting the memory device of FIG. 3(A);

FIG. 5 is a block diagram of a memory card using a partial product ofthe flash memory of FIG. 1;

FIG. 6 is a block diagram of a memory card using four complete compositeconforming circuits of the flash memory of FIG. 1;

FIG. 7 is a diagram showing the operation of a memory card;

FIG. 8 is a block diagram of a memory card constituted by using apartial product of a flash memory not provided with a circuit structurefor selectively inhibiting access to the memory block of FIG. 1;

FIG. 9 is schematic circuit diagram showing a system for processing aready/busy signal of the memory card of FIG. 5;

FIG. 10 is a block diagram of a flash memory representing a secondembodiment of the present invention;

FIG. 11(A) is a circuit diagram of a memory cell used for a flash memoryand

FIG. 11(B) is a characteristic diagram relating thereto;

FIG. 12 is a circuit diagram showing a basic structure of a memory cellarray of a flash memory;

FIG. 13 is a chart showing the voltage condition of the erase operationand write operation of a memory cell;

FIG. 14 is a circuit diagram of the write erase control circuit, memoryblock, and input/output circuit described referring to FIG. 1;

FIG. 15 is a block diagram of a flash memory representing a thirdembodiment of the present invention;

FIG. 16 is a circuit diagram showing a circuit for inhibiting the outputoperation of a data input/output buffer 7 in accordance with the setstate of a fuse program circuit;

FIG. 17 is a circuit diagram showing a circuit for inhibiting theoperation of an erase control circuit in accordance with the set stateof a fuse program circuit;

FIG. 18 is a circuit diagram showing a circuit for inhibiting theoperation of an erase verify control circuit in accordance with the setstate of a fuse program circuit;

FIG. 19 is a circuit diagram showing a circuit for inhibiting theoperation of a write control circuit in accordance with the set state ofa fuse program circuit;

FIG. 20 is a circuit diagram showing a circuit for selectivelyinhibiting the operation of a write verify circuit in accordance withthe set state of a fuse program circuit;

FIG. 21 is a circuit diagram showing an inhibit condition decisioncircuit;

FIG. 22 is a circuit diagram showing an erase verify decision circuit;

FIG. 23 is a circuit diagram showing a write verify decision circuit;

FIG. 24 is a flowchart schematically showing the fabrication process ofa flash memory;

FIG. 25(A) is a diagram of an address map,

FIG. 25(B) is a diagram of is a flash memory, and

FIG. 25(C) is a flowchart showing the erase operation of a completecomposite conforming circuit of the flash memory shown in FIG. 15;

FIG. 26(A) is a diagram of an address map,

FIG. 26(B) is a diagram of a flash memory, and

FIG. 26(C) is a flowchart showing the erase operation of a low-orderpartial product of the flash memory shown in FIG. 15;

FIG. 27(A) is a diagram of an address map,

FIG. 27(B) is a diagram of a flash memory, and

FIG. 27(C) is a flowchart showing the erase operation of a high-orderpartial product of the flash memory shown in FIG. 15;

FIG. 28(A) is a diagram of an address map,

FIG. 28(B) is a diagram of a flash memory, and

FIG. 28(C) is a flowchart showing the write operation of a completecomposite conforming circuit of the flash memory shown in FIG. 15;

FIG. 29(A) is a diagram of an address map,

FIG. 29(B) is a diagram of a flash memory, and

FIG. 29(C) is a flowchart showing the write operation of a low-orderpartial product of the flash memory shown in FIG. 15;

FIG. 30(A) is a diagram of an address map,

FIG. 30(B) is a diagram of a flash memory, and

FIG. 30(C) is a flowchart showing the write operation of a high-orderpartial product of the flash memory shown in FIG. 15;

FIG. 31 is a block diagram of a flash memory representing a fourthembodiment of the present invention;

FIG. 32 is a circuit diagram showing another example of a circuit forinhibiting the output operation of a data input/output buffer inaccordance with the set state of a fuse program circuit;

FIG. 33 is a circuit diagram showing still another example of a circuitfor inhibiting the operation of an erase control circuit in accordancewith the set state of a fuse program circuit;

FIG. 34 is a circuit diagram showing yet another example of a circuitfor inhibiting the operation of an erase verify control circuit inaccordance with the set state of a fuse program circuit;

FIG. 35 is a circuit diagram showing still another example of a circuitfor inhibiting the operation of a write control circuit in accordancewith the set state of a fuse program circuit;

FIG. 36 is a circuit diagram showing a further example of a circuit forselectively inhibiting the operation of a write verify control circuitin accordance with the set state of a fuse program circuit:

FIG. 37(A) is a diagram of an address map,

FIG. 37(B) is a diagram of a flash memory, and

FIG. 37(C) is a flowchart showing the erase operation of a completecomposite conforming circuit of the flash memory shown in FIG. 31;

FIG. 38(A) is a diagram of an address map,

FIG. 38(B) is a diagram of a flash memory, and

FIG. 38(C) is a flowchart showing the erase operation for a low-orderpartial product of the flash memory shown in FIG. 31;

FIG. 39(A) is a diagram of an address map,

FIG. 39(B) is a diagram of a flash memory, and

FIG. 39(C) is a flowchart showing the erase operation of a high-orderpartial product of the flash memory shown in FIG. 31;

FIG. 40(A) is a diagram of an address map,

FIG. 40(B) is a diagram of a flash memory, and

FIG. 40(C) is a flowchart showing the write operation of a completecomposite conforming circuit of the flash memory shown in FIG. 31;

FIG. 41(A) is a diagram of an address map,

FIG. 41(B) is a diagram of a flash memory, and

FIG. 41(C) is a flowchart showing the write operation of a low-orderpartial product of the flash memory shown in FIG. 31; and

FIG. 42(A) is a diagram of an address map,

FIG. 42(B) is a diagram of a flash memory, and

FIG. 42(C) is a flowchart showing the write operation of a high-orderpartial product of the flash memory shown in FIG. 31.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a block diagram showing the flash memory 1 representing anembodiment of the present invention. The flash memory shown in FIG. 1 isformed on a semiconductor substrate made of, for example, single-crystalsilicon using a semiconductor integrated circuit fabrication technique.The flash memory 1 of this embodiment is provided with two memory blocks2 and 3 in each of which electrically erasable nonvolatile memory cellsare arranged in the form of a matrix.

In the case of this embodiment, 8 bits (1 byte) are used as a data writeunit and a data read unit for each of the memory blocks 2 and 3.Transfer of data to and from the memory blocks 2 and 3 is performed inunits of a byte by input/output circuits 4 and 5. Either of theinput/output circuits 4 and 5 is connected to a data input/output buffer7 through a selector 6. The data input/output buffer 7 is connected to8-bit external-data input/output terminals 8 through which data istransferred to and from an external unit. Address signals A0 to A20 forselecting memory cells are supplied to the memory blocks 2 and 3 throughan address input buffer 10. The address input buffer 10 has a functionof serving as an address latch circuit and, for example, directly holdsa write address so that the address can be used as a write verifyaddress. In this case, the address signals A0 to A20 are regarded asaddress signals for designating word addresses, that is, word-size data.The address signal A0 is regarded as an address signal representingwhich byte-size data is designated in word-size data. Though theinvention is not so restricted, the address signal A0 is regarded as anaddress signal for designating which memory block is selected out of thememory blocks 2 and 3. In the case of this embodiment, each of thememory blocks 2 and 3 has a memory capacity of 1M bytes.

In FIG. 1, symbol 11 denotes first control means for controlling thewriting of information into and the reading of information from thememory blocks 2 and 3 in accordance with an instruction sent from anexternal unit and for outputting a ready/busy signal MR/B representingthe completion of a write operation in response to an instruction for awrite operation. The first control means 11, though not so restricted,comprises a write erase control circuit 12 exclusively used for a memoryblock 2, a write erase control circuit 13 exclusively used for a memoryblock 3, and a timing controller 14 for controlling the entire flashmemory. Each of the write erase control circuits 12 and 13 is providedwith a control circuit and a decision circuit for erase verify and writeverify. The timing controller 14 receives a typically-shown outputenable signal MOE, a write enable signal MWE, and a chip enable signalMCE as external access control signals. The timing controller 14 has acommand register 15 in which a command supplied from an external unitthrough the data input/output buffer 7 is set and operation modes suchas erase verify, write, and write verify are set by decoding thecommand. Though the invention is not so restricted, the control signalMWE represents an instruction to write a command into the commandregister. The control signal MOE represents an instruction to execute aread operation. The control signal MCE represents an instruction toselect a chip.

The erase operation can be performed for every block or every 512 bytes.Though the invention is not so restricted, designation of a block to beerased is performed by the 11-bit address signals A10 to A20 and the1-bit address signal A0. That is, when writing an erase command into thecommand register 15, the address signals A0 and A10 to A20 are capturedby an erase block designation register 16. The timing controller 14generates an internal control signal for simultaneously erasing512-byte-blocks designated by A10 to A20 for one memory block designatedby the address signal A0 captured by the erase block designationregister 16.

In the case of this embodiment, the least-significant address signal A0is regarded as a signal for selecting a memory block 2 or 3 inaccordance with the logical value of the signal A0. Symbols a0, a0*(symbol "*" denotes inversion), a1, a1* to a20, and a20* are internalcomplementary address signals corresponding to A0 to A20. The timingcontroller 14 controls whether to execute a read operation or a writeoperation of either of the memory blocks 2 and 3 and moreover, controlsto which circuit the input/output circuit 4 or 5 a selection circuit 6should be connected to, referring to the internal complementary addresssignals a0 and a0*. The reference numeral 20 generally denotesinformation including control signals transferred between the writeerase control circuit 12 and the timing controller 14, the referencenumeral 21 generally denotes information including control signalstransferred between the write erase control circuit 13 and the timingcontroller 14, the reference numeral 22 denotes a control signal for theinput/output circuit 4, the reference numeral 23 denotes a controlsignal for the input/output circuit 5, and the reference numeral 24denotes a control signal for the selection circuit 6.

The flash memory 1, according to the present invention, is used as apartial product when either of the memory blocks 2 and 3 has anirremediable defect. A flash memory in which neither memory block 2 normemory block 3 have an irremediable defect is referred to as a completecomposite conforming circuit. This embodiment is provided with a fuseprogram circuit 30 in which information for designating a defectivememory block out of the memory blocks 2 and 3 is set, a fuse programcircuit 31 in which information representing that the memory is apartial product is set, and an inhibition controller 32 which operatesto allow two partial products to be completely compatible with acomplete composite conforming circuit. The inhibition controller 32receives the complementary internal address signal a0 (a0*) and outputsof the fuse program circuits 30 and 31.

The inhibition controller 32 controls an inhibit control signal 33 to anactivation level when a memory block regarded as selected by thecomplementary internal address signal a0 (a0*) coincides with a memoryblock designated by the fuse program circuit 30 if the output of thefuse program circuit 31 indicates that the memory is a partial product.That is, the inhibition controller 32 serves as detection means fordetecting an access to a defective memory block designated by the fuseprogram circuit 30 in accordance with an address signal.

The timing controller 14, in response to receipt of the inhibit controlsignal 33, inhibits an information rewrite operation of the memory blockconcerned in response to an instruction for an information rewriteoperation of a memory cell when the signal 33 is activated, and,moreover, inhibits the data output operation of the data input/outputbuffer 7 in response to an instruction for an information read operationof a memory cell or the like. The timing controller 14 brings aready/busy signal MR/B to a ready state and outputs the signal to anexternal unit when inhibiting the information rewrite operation of thememory block. The ready-state ready/busy signal MR/B is regarded as astatus signal representing the completion of the rewrite operation.Moreover, the timing controller 14 is finally brought to a ready stateeven if the ready/busy signal MR/B is instantaneously brought to a busystate in a very short period until the logical operation according tothe activation-level inhibit control signal 33 is determined.

FIG. 2 shows an example of the address input buffer 10. The bits of theaddress signals A1 to A20 are converted into non-inverted internalcomplementary address signals a1 to a20 through four-stage invertersINV1, INV2, INV3, and INV4, and, moreover, they are also converted intoinverted internal complementary address signals a1* to a20* throughthree-stage inverters INV1, INV2, and INV3. In this case, atwo-input-type exclusive NOR gate 104 is provided at the second stagefor receiving the address signal A0 instead of the inverter INV2, andthe output of the fuse program circuit 34 is supplied to the inputterminal of the exclusive NOR gate 104 so that the logical values of theinternal complementary address signals a0 and a0* can be selectivelyinverted for the logical value of the address signal A0 in accordancewith the output logical value of the fuse program circuit 34. That is,the logical value of the internal complementary address signal a0 ismade to coincide with the logical value of the address signal A0 whenthe set value of the fuse program circuit 34 is "1" and the logicalvalue of the internal complementary address signal a0 is made to beopposite to the logical value of the address signal A0 when the setvalue of the fuse program circuit 34 is "0".

The timing controller 14 shown in FIG. 1 selects the operation of thememory block 2 when the logical value of the internal complementaryaddress signal a0 is "0" and connects the input/output circuit 4 to thedata input/output buffer 7 to allow the circuit 4 to be controlled bythe selection circuit 6. When the logical value of the internalcomplementary address signal a0 is "1", the operation of the memoryblock 3 is selected and the input/output circuit 5 is connected to thedata input/output buffer 7 and controlled by the selection circuit 6.For example, when the memory block 2 has an irremediable defect, thelogical value "0" is set in the fuse program circuit 30. When thelogical value of the internal complementary address signal a0 is set at"0" in the above state, the inhibit control signal 33 is set at anactivation level. In this case, if an instruction to execute theinformation rewrite operation of a memory cell is given, the informationrewrite operation of the memory block 2 responding to the instruction isinhibited. Moreover, if an instruction to execute the information readoperation for a memory cell is given, the data output operation of thedata input/output buffer 7 responding to the instruction is inhibited.In this case, if the set value of the fuse program circuit 34 is "1",the inhibit operation of the memory block 2 is performed for an accesssuch that the logical value of the address signal A0 is set at "0".However, if the set value of the fuse program circuit 34 is "0", theinhibit operation of the memory block 2 is performed for an access suchthat the logical value of the address signal A0 is set at "1".

As understood from the foregoing description of the embodiment, when thememory block selected in accordance with the address signals A0 to A20supplied from an external unit coincide with the memory block (defectivememory block in a partial product) designated by the fuse programcircuit 30, and, moreover, an instruction to execute an informationrewrite operation of a memory cell is given, the information rewriteoperation of the memory block concerned responding to the instruction isinhibited by the inhibition controller 32. Moreover, when an instructionto execute the information read operation for a memory cell or the likeis given, the data output operation of the data input/output buffer 7responding to the instruction is inhibited by the inhibition controller32. Thus, the inhibiting function of the flash memory 1 used as apartial product makes it possible to use a partial product of the flashmemory chip as it is on a system on which the flash memory 1 is mountedwithout externally requiring a terminal of the flash memory 1 forinputting the specific address signal A0 to a certain level inaccordance with the address arrangement of a defective memory block.

FIG. 3(A) shows an embodiment of a memory device using a flash memory asa partial product as described with reference to FIG. 1. The memorydevice 40 shown in FIG. 3(A) uses two flash memories 1 as partialproducts, in which external terminals corresponding to each of thememories 1 are connected in common and connected to a respective leadterminal P of a package 41. One flash memory is denoted by 1-L and theother flash memory is denoted by 1-U. For example, the flash memory 1-Lis a flash memory fuse-programmed so that one normal memory block isaccessed when the address signal A0 having a logical value "0", and theaccess to the other defective memory block is inhibited when the signalA0 has a logical value "1". The flash memory 1-L is also merely referredto as a low-order partial product. However, the flash memory 1-U is aflash memory fuse-programmed so that one normal memory block is accessedwhen the address signal A0 has a logical value "1" and the access to theother defective memory block is inhibited when the signal A0 has alogical value "0". The flash memory 1-U is also merely referred to as ahigh-order partial product. As understood from the description of thefuse program circuit 34, it is unnecessary for the normal memory blockof the low-order partial product 1-L to be physically different fromthat of the high order partial product 1-U, and the address arrangementof a normal memory block for the address signal A0 is determined by theset value of the fuse program circuit 34. Therefore, even if a biasoccurs in defective portions of a plurality of partial products clue tothe fabrication process, it is possible to apparently optionally changethe arrangement of an operable memory block for the address signal A0supplied from an external unit by determining the set value of the fuseprogram circuit 34 of each partial product corresponding to the degreeof the bias. Thereby, even when a memory device 40 substituted for anon-defective product is fabricated by combining partial products whoseoperational regions are complementary, it is possible to prevent thepossibility that defective partial products of one defect type more thanthe other defect type are left unused.

In the case of the embodiment of FIG. 3(A), OE (input terminal of MOE),WE (input terminal of MWE), CE (input terminal of MCE), R/B (outputterminal of MR/B), DAT (data input/output terminal 8), and address inputterminals A0 to A20 are typically shown as external terminals connectedbetween partial products in common. Though no power supply terminal isillustrated, corresponding power supply terminals of the partialproducts are connected in common. In this case, a ready/busy signal MR/Bof a flash memory is generated by an open drain circuit and outputterminals are wired-OR-connected to each other.

The memory device using the high-order partial product 1-U and thelow-order partial product 1-L shown in FIG. 3(A) are complementarilyoperated in accordance with the logical value of the address signal A0supplied to the memory device, as understood from the description withreference to FIG. 1. Therefore, as shown in FIG. 3(B), addresses 0, 2,4, . . . are practically mapped in the low-order partial product 1-L andaddresses 1, 3, 5, . . . are practically mapped in the high-orderpartial product 1-U. The entire memory capacity of the memory device andthe external terminal structure of the package are the same as those ofthe flash memory 1-P used as a complete composite conforming circuit inwhich both memory blocks do not have any irremediable defect and thehandling of the memory device for the address signal A0 is the same asthat of the complete composite conforming circuit 1-P. Therefore, inthese points, the memory device of FIG. 3(B) has complete compatibilitywith the complete composite conforming circuit 1-P.

FIG. 4 shows an example of a logic circuit for generating a ready/busysignal and a ready/busy status of the partial products 1-L and 1-Uconstituting the memory device 40. The ready/busy terminals R/B of thepartial products 1-L and 1-U are connected to an open drain circuit ineach flash memory chip. That is, an N-channel MOS transistor 36switch-controlled by the output of a busy status generator 140 isincluded, and the source of the transistor 36 is connected to a groundterminal GND and the drain is connected to a power supply terminal Vccthrough a resistor 35.

The busy status generator 140 is included in the timing controller 14 ofFIG. 1 to keep the MOS transistor 36 on until a designated operation iscompleted when the erase mode or write mode is designated. When therewrite operation is inhibited by the inhibit signal 33, the busy statusgenerator 140 sets the output at a low level interlockingly with theinhibition of the erase or write operation. That is, when the access toa defective memory block is detected, the busy status generator 140operates as means for making it possible to output a status representingthe completion of a data rewrite operation for an instruction for a datarewrite operation irrespective of the completion of the operation.

The gate control signal of the MOS transistor 36 is supplied to a statusregister 141 to generate a ready/busy flag RBF. The ready/busy flag RBFrepresents a busy state when the logical value is "1" and a ready statewhen the logical value is "0". The value of the status register 141 ismade readable by an external unit through the data input/output buffer7. FIG. 4 typically shows only the read path of the ready/busy flag RBF.A two-input-type OR gate 143 is provided in the read path of theready/busy flag RBF, the ready/busy flag RBF is supplied to one input ofthe gate and the drain of the MOS transistor 36 is connected to theother input through an inverter 142. The ready/busy terminal R/B of thehigh-order partial product 1-U and that of the low-order partial product1-L are wired-OR-connected to each other and connected to an externalready/busy terminal PR/B of the package.

During an erase or write of data, the busy status generator 140 keepsthe MOS transistor 36 on. Thereby, the ready/busy flag RBF is set at alogical value "1". The ready/busy state of the flash memory 1-L or 1-ucan be recognized by externally referring to the ready/busy terminalR/B. Moreover, unless the data input/output buffer 7 is operated, it ispossible to externally recognize the ready/busy state by externallyreading the value of the status register L4. In the case of the memorydevice 40, the operation of the memory blocks, i.e. the high-orderpartial product 1-U and the low-order partial product 1-L, areselectively inhibited in accordance with the value of A0. An externalread of the status register 140 can be made possible by activating thecontrol signal MOE. In this case, however, the status register 141, aread object, is made possible for both the partial products 1-L and 1-Udepending on the value of A0. As a result of comparison of the internalstate of a partial product whose operation is inhibited by A0 with thatof a partial product whose operation is not inhibited by A0, the partialproduct whose operation is inhibited is brought to a ready state whenthe partial product whose operation is not inhibited is in a busy state.In this case, the terminal PR/B is in a busy state because the terminalsR/B of both partial products are wired-OR-connected. However, theready/busy flags RBF represent the actual internal states of the partialproducts. That is, the flag RBF of the partial product whose operationis inhibited is brought to a ready state and the flag RBF of the partialproduct whose operation is not inhibited is brought to a busy state. Inthis case, because the OR gate 143 is provided in the output path of theready/busy flag RBF, the output of the OR gate 143 is forcedly broughtto a busy state (logical value "1") when the other partial product is ina busy state even if the ready/busy flag RBF represents a ready state(logical value "0"). Therefore, when the terminal PR/B of the memorydevice 40 is in a busy state (logical value "0"), it is possible to setup a busy state (logical value "1") even if the ready/busy flag RBF ofthe partial product whose operation is inhibited is read by an externalunit. If the OR gate 143 is not provided in the output path of theready/busy flag RBF, a ready state is set up by reading the ready/busyflag RBF of the partial product whose operation is inhibited to anexternal unit and a busy state is set up by reading the ready/busy flagRBF of the partial product whose operation is not inhibited to anexternal unit, and, thus, both flags RBF do not coincide with eachother. Therefore, by using the structure in FIG. 4, the state of aready/busy flag read out to an external unit becomes the same as thecase of a complete composite conforming circuit, and, also in thispoint, complete compatibility with the complete composite conformingcircuit is realized.

FIG. 5 shows an embodiment of a memory card. The memory card 50 of thisembodiment is provided with four low-order partial products 1-L and fourhigh-order partial products 1-U. Though the invention is not sorestricted, the partial products 1-L and 1-U each have an effectivememory capacity of 1M bytes. FIG. 6 shows a memory card 51 using fourcomplete composite conforming circuits 1-P each having a memory capacityof 2M bytes. In the description of the memory card, lhe low-orderpartial product 1-L, the high-order partial product 1-U, and thecomplete composite conforming circuit 1-P are each provided with an8-bit data input/output terminal.

In FIG. 5, symbol 52 denotes a card controller and symbol 53 denotes apower supply circuit. The card controller 52 receives address signalsSA0 to SA24 and various control signals SCONT, outputs a busy signalSBSY, and receives/outputs data values SD0 to SD15. The power supplycircuit 53 has an input terminal for a power supply voltage Vcc, such as5 V, and a rewriting high voltage Vpp, such as 12 V, and moreover has acircuit like a DC--DC converter for generating a writing high voltage byboosting the Vcc, unless Vpp is supplied from an external unit. When Vppis supplied from an external unit, the voltage boosting function is notused.

The memory card 50 of this embodiment has four memory pairs M1 to M4each of which is constituted by pairing a low-order partial product 1-Land a high-order partial product 1-U. Though each memory pair ispractically the same as the memory device 40 in FIG. 3(A), it isunnecessary to package the memory pairs. The memory card 50 transfersdata to and from an external unit word by word. The memory pairs M2 andM4 are made to correspond to low-order byte data SD0 to SD7 throughlow-order data buses MD0 to MD7. The memory pairs M1 and M3 are made tocorrespond to high-order byte data SD8 to SD15 through high-order databuses MD8 to MD15. Address buses MA0 to MA20 are connected to addressinput terminals (A0 to A20) of partial memories of the memory pairs M1to M4 in common. An output enable signal MOE and a write enable signalMWE are supplied to respective terminals OE and WE of partial memoriesof the memory pairs M1 to M4 in common. A chip enable signal MCE0 issupplied to the partial memories of the memory pairs M1 and M2 in commonand a chip enable signal MCE1 is supplied to the partial memories of thememory pairs M3 and M4 in common. Ready/busy terminals R/B of partialmemories are connected in common for every memory pair and are connectedto the card controller 52. Moreover, for the signal wiring for the abovedata values, addresses and various control signals, the wiring formed ona not-illustrated card substrate is used.

The card controller 52 performs access control of the memory pairs M1 toM4 in accordance with the instruction from a host processor or the likethrough a not-illustrated card interface connected with the controller52. For example, the instruction from the host processor is a commandand is fetched by a not-illustrated command register. The contents ofthe instruction include read, erase, and write for a memory pair. Anaccess object is specified by an address signal. Though the invention isnot so restricted, SA0 to SA20 among the above address signals SA0 toSA24 are fed to A0 to A20. SA21 is supplied to a decoder 54 and the chipenable signals MCE0 and MCE1 are generated in accordance with thelogical value of SA21.

The memory card 50 of FIG. 5 is different from the memory card 51 usingthe complete composite conforming circuit 1-P shown in FIG. 6 only inthat a high-order partial product 1-U and a low-order partial product1-L are used. This is because the memory pairs M1 to M4 are completelycompatible with a complete composite conforming circuit 1-P asunderstood from the description with reference to FIG. 3(A).

FIG. 7 shows the operation of the memory card 50. FIG. 7 typically showsthe memory pairs M1 and M2. For example, in the case of the low-orderpartial product 1-L, the inhibit control signal 33 is activated when theaddress signal A0 has a logical value "1", and the rewrite operation ofthe memory block 3 and the external output of read data included in thesignal 33 are inhibited. Moreover, in the case of the high-order partialproduct 1-U, the inhibit control signal 33 is activated when the addresssignal A0 has a logical value "0", and the rewrite operation of thememory block 2 and the external output of read data included in thesignal 33 are inhibited. When the chip enable signal MCE0 is set at theselection level, the partial products 1-U and 1-L of each of the memorypairs M1 and M2 are brought into an operable state. In this case, whenword addresses A1 to A20 specify the address 0 of each partial product,and when A0 serving as a byte specifying address is set at a logicalvalue "0", the rewrite operation of the memory block 2 and the externaloutput of read data are inhibited and the substantial access operationis performed only by the low-order partial product 1-L. Thereby, theaddress 1 of the high-order partial product 1-U of each of the memorypairs M1 and M2 is accessed.

For the case of the high-order partial product 1-U and low-order partialproduct 1-L thus chip-selected in parallel, a substantial accessoperation is alternately performed in accordance with a change oflogical values of A0. Therefore, the memory card 51 comprising only acomplete composite conforming circuit and the memory card 50 using thepartial products 1-L and 1-U can mutually perform the same operationapparently (in terms of external specifications) even if the same cardcontroller 52 is used. That is, the control of the memory card 50 andthat of the memory card 51 by an external unit can be completelyidentical.

To constitute such a memory card 61 by using fuse program circuits 30and 31 for selectively inhibiting the access to the memory blocks 2 and3 and a partial product of a flash memory not provided with a controller32, it is necessary to use the circuit structure shown in FIG. 8. Thatis, it is necessary to fixedly inhibit the selection of the memory block3 by connecting the address A0 to the ground terminal GND in the case ofa low-order partial product 60-L and fixedly inhibit the selection ofthe memory block 2 by connecting the address A0 to the power supplyterminal Vcc in the case of a high-order partial product 60-H. In thiscase, it is necessary to separately chip-selection-control thehigh-order partial product 60-H and low-order partial product 60-Lconstituting a memory pair, otherwise data collision occurs between thepartial products 60-H and 60-L. Therefore, in the memory card in FIG. 8,four lines MCE1 to MCE4 are needed for a chip enable signal, and, in acard controller 62, a decoder 63 having logic different from that of thememory cards in FIGS. 5 and 6 is needed. For example, in the decoder 63,an address SA0 for chip selection is needed.

FIG. 9 shows a system for processing a ready/busy signal in the memorycard 50. The ready/busy terminals R/B of the partial products 1-L and1-U are connected to an open drain circuit inside the card 50. Thecircuit structure used is, for example, the one shown in FIG. 4. Aready/busy signal MR/B1 is exclusively used for the memory pair M1, aready/busy signal MR/B2 is exclusively used for the memory pair M2, aready/busy signal MR/B3 is exclusively used for the memory pair M3, anda ready/busy signal MR/B4 is exclusively used for the memory pair 4.Moreover, these signals MR/B1 to MR/B4 are connected to correspondingbits of a status register 56 provided in the card controller 52. Theready/busy signals MR/B1 and MR/B2 are connected to the inputs of atwo-input-type AND gate 59 and the ready/busy signals MR/B3 and MR/B4are connected to the inputs of a two-input-type AND gate 58. The outputsof the AND gates 58 and 59 are connected to the inputs of atwo-input-type AND gate 57, and the output of the AND gate 57 issupplied to an external unit as the busy signal SBSY and is alsosupplied to the corresponding bit of a card status register 55. The busysignal SBSY at high level reports to an external unit that the memorycard 50 is in a ready state.

FIG. 10 shows a flash memory representing a second embodiment of thepresent invention. The flash memory 1A of FIG. 10 is formed on asemiconductor substrate made of single-crystal silicon using asemiconductor integrated circuit fabrication technique. The flash memory1A of FIG. 10 is provided with two memory blocks 72 and 73 in whichelectrically erasable nonvolatile memory cells are arranged in the formof a matrix. In the case of this embodiment, data is written in or readfrom each of the memory blocks 72 and 73 every 4 bits. Data is input toor output from the memory blocks 72 and 73 by input/output circuits 74and 75 every 4 bits. The input/output circuits 74 and 75 are connectedto exclusive data input/output buffers 77L and 77U, respectively. Thedata input/output buffers 77L and 77U are connected to 4-bit exclusiveexternal-data input/output terminals 78L and 78U, respectively, throughwhich data is transferred to and from an external unit. Address signalsA0 to A20 for selecting memory cells are supplied to the memory blocks72 and 73 from external address input terminals 79 through an addressinput buffer 80. In the case of this embodiment, the memory blocks 72and 73 each have a memory capacity of 1M bytes.

In FIG. 10, symbol 81 denotes first control means for controlling therewrite and read of information into and from the memory blocks inaccordance with the instruction from an external unit and for outputtinga ready/busy signal MR/B representing the completion of a rewriteoperation in response to an instruction for a rewrite operation to anexternal unit. The first control means 81 comprises a write erasecontrol circuit 82 exclusively used for the memory block 72, a writeerase control circuit 83 exclusively used for the memory block 73, and atiming controller 84 for controlling the whole of the flash memory. Thetiming controller 84 receives output enable signal MOE, write enablesignal MWE, and chip enable signal MCE, typically shown as externalaccess control signals. The timing controller 84 has a command register85 to which a command supplied from an external unit through the datainput/output buffer 77L or 77U and operation modes, such as erase, eraseverify, write, and write verify, are set by decoding the command. Thoughthe invention is not so restricted, the control signal MWE gives aninstruction to write a command into the command register. The controlsignal MOE gives an instruction for a read operation. The control signalMCE gives an instruction for chip selection.

The erase operation can be performed every block or every 512 bytes.Designation of a block to be erased, though the invention is not sorestricted, is performed by 11-bit address signals A10 to A20. That is,when an erase command is written in the command register 85, the addresssignals A10 to A20 are captured by an erase block designation register86. The timing controller 84 generates an internal control signal forsimultaneously erasing 512-byte memory blocks designated by the addresssignals A10 to A20 captured by the erase block designation register 86.

In the case of this embodiment, unless the memory block 72 or 73 has anyirremediable defect, the timing controller 84 controls the operation ofthe memory blocks 72 and 73 in parallel. The reference numeral 90denotes a control signal for the write erase control circuit 82, thereference numeral 91 denotes a control signal for the write erasecontrol circuit 83, the reference numeral 92 denotes a control signalfor the input/output circuit 74, the reference numeral 93 denotes acontrol signal for the input/output circuit 75, the reference numeral 94denotes a control signal for the data input/output buffer 77L, and thereference numeral 95 denotes a control signal for the data input/outputbuffer 77U.

The flash memory of this embodiment is used as a partial product wheneither of the memory blocks 72 and 73 has an irremediable defect. Thisembodiment is provided with a fuse program circuit 100 to whichinformation for designating a defective memory block out of the memoryblocks 72 and 73 is set, a fuse program circuit 101 to which informationrepresenting a partial product is set, and an inhibition controller 102which operates to make two partial products completely compatible with acomplete composite conforming circuit. The inhibition controller 102generates an inhibit control signal 33A for allowing the timingcontroller 84 to inhibit the write operation of a memory blockdesignated by the fuse program circuit 100 and the data output operationof the data input/output buffer corresponding to the memory block onlywhen the output of the fuse program circuit 101 represents a partialproduct. The timing controller 84 for receiving the inhibit controlsignal 33A, when inhibition of the operation of the memory block 72 isordered by the signal 33A, keeps the erase control circuit 82 inactive,keeps the input/output circuit 74 inactive (for example, keeps a senseamplifier inactive), and keeps the data input/output buffer 78L in ahigh-impedance state with the control signals 90, 92, and 94. Wheninhibition of the operation of the memory block 73 is ordered for thetiming controller 84 by the inhibit control signal 33A, the controller84 keeps the write erase control circuit 83 inactive, keeps theinput/output circuit 75 inactive (for example, keeps a sense amplifierinactive), and keeps the data input/output buffer 78U in ahigh-impedance state with the control signals 91, 93, and 95. Thepartial product of the flash memory of this embodiment also can be usedfor a memory device, like the memory device in FIG. 3(A).

FIG. 11(A) shows a memory cell structure of a flash memory. The memorycell typically shown in FIG. 11(A) comprises an insulating-gate-typefield effect transistor having a two-layer gate structure. In FIG.11(A), reference numeral 201 denotes a P-type silicon substrate,reference numeral 202 denotes a P-type semiconductor region formed onthe silicon substrate 1, and reference numeral 203 and 204 denote N-typesemiconductor regions. Reference numeral 205 denotes the floating gateformed on the P-type silicon substrate 201 through a thin oxide film 206(the thickness is, e.g., 10 nm) serving as a tunnel insulting film, andreference numeral 207 denotes the control gate formed on the floatinggate 205 through an oxide film 208. The source comprises an N-typesemiconductor region 204 and the drain comprises an N-type semiconductorregion 203 and a P-type semiconductor region 202. The information storedin the memory cell is substantially held by the transistor as the changeof a threshold voltage. A case in which a transistor for storinginformation (hereafter also referred to as memory cell transistor) is ofthe N-channel type, unless otherwise indicated, will be described below.

The operation for writing information into a memory cell is realized byapplying a high voltage to the control gate 207 and the drain andinjecting electrons into the floating gate 205 from the drain side byavalanche injection. As a result of such a write operation, thethreshold voltage of a memory transistor viewed from the control gate207 of the transistor rises compared to the memory transistor in anerase state when the write operation is not performed.

The erase operation is realized by extracting electrons from thefloating gate 205 to the source side by exploiting the tunnelphenomenon. As shown in FIG. 11(B), the threshold voltage of the memorytransistor viewed from the control gate 207 of the transistor is loweredthrough the erase operation. In FIG. 11(B), the threshold of the memorycell transistor is set at a positive voltage level in both the writestate and the erase state. That is, the threshold voltage in the writestate is raised and the threshold voltage in the erase state is loweredfor the word-line selection level supplied from a word line to thecontrol gate 207. When both threshold voltages and the word-lineselection level are in the above relation, it is possible to constitutea memory cell with a transistor without using a selection transistor.When electrically erasing stored information, the stored information iserased by extracting electrons accumulated in the floating gate 205 tothe source electrode. Therefore, when the erase operation is continuedfor a relatively long time, electrons in an amount more than theelectrons injected into the floating gate 205 are extracted when thewrite operation is performed. Therefore, when excessive erasing, inwhich electrical erasing is continued for a relatively long time, isperformed, the threshold voltage of the memory cell transistor is set ata negative level and a failure occurs in that a word line is selectedeven at a non-selection level. Moreover, the write operation can beperformed by using a tunnel current similar to the case of the eraseoperation.

In the case of a read operation, the voltages to be applied to the drainand control gate 207 are limited to relatively low values so that a weakwrite may not be performed for the above memory cell, that is, undesiredcarrier injection into the floating gate 205 is not performed. Forexample, a low voltage of approx. 1 V is applied to the drain, and,moreover, a low voltage of approx. 5 V is applied to the control gate207. By detecting the magnitude of a channel current flowing through thememory cell transistor with the above applied voltages, it is possibleto judge whether the logical value "0" or "1" of the information isstored in the memory cells.

FIG. 12 shows a schematic diagram of a memory cell array using the abovememory cell transistor. FIG. 12 typically shows four memory celltransistors Q1 to Q4. In the case of memory cells arranged in X and Ydirections, the control gates (memory cell selection gate) of the memorycell transistors Q1 and Q2 (Q3 and Q4) arranged in the same row areconnected to a corresponding word line WL1 (WL2), and the drain regions(input/output nodes of memory cells) of the memory transistors Q1 and Q3(Q2 and Q4) are connected to a corresponding data line DL1 (DL2). Thesource regions of the memory transistors Q1 and Q3 (Q2 and Q4) areconnected to a source line SL1 (SL2).

FIG. 13 shows a voltage condition for the erase operation and writeoperation of a memory cell. In FIG. 13, the memory cell is constitutedby a memory cell transistor and the gate is a control gate serving as agate for selecting the memory cell transistor. In FIG. 13, fornegative-voltage-type erasing, a high electric field necessary for theerasing is generated by applying a negative voltage such as -10 V to acontrol gate. As understood from the voltage condition illustrated inFIG. 13, it is possible to simultaneously erase memory cells to which atleast the source is connected in common in the case ofpositive-voltage-type erasing. Therefore, in the case of the structurein FIG. 12, when the source lines SL1 and SL2 are connected, four memorycells Q1 to Q4 can be simultaneously erased. In this case, by changingthe number of memory cell transistors connected to the same source line,it is possible to optionally determine the size of a memory block.Source line dividing methods include a method of using a data line as aunit (common source line is extended in the data line direction), asillustrated in FIG. 14, and a method of using a word line as a unitcommon source line is extended in the word line direction). Moreover, inthe case of negative-voltage-type erasing, it is possible tosimultaneously erase the memory cells to which the control gate isconnected in common.

FIG. 14 shows the write erase control circuit 12, memory block 2, andinput/output circuit 4 described with reference to FIG. 1. The memoryblock 2 has 8-bit data terminals D0 to D7 and memory arrays ARY0 to ARY7for every data terminal. Each of the memory arrays ARY0 to ARY7, thoughthe invention is not so restricted, is divided into two parts forsimultaneous erasing of blocks having the source lines SL1 connected incommon. Though FIG. 14 typically shows details of only the memory arrayARY0, other memory arrays ARY1 to ARY7 also have the same structure asthe memory array ARY0.

Memory cells MC each comprising an insulating-gate-type field effecttransistor having a two-layer gate structure described, as withreference to FIG. 11(A) are arranged on each of the memory arrays ARY0to ARY7 like a matrix. In FIG. 14, WLO to WLn denote word lines commonto all memory arrays ARY0 to ARY7. Control gates of the memory cellsarranged in the same row are connected to corresponding word lines. Ineach of the memory arrays ARY0 to ARY7, the drain regions of the memorycells MC arranged in the same column are connected to corresponding datalines DLO to DLn. Moreover, the source regions of the memory cells MCconstituting one simultaneous erasing block are connected to the sourceline SL1 in common and the source regions of the memory cells MCconstituting the other simultaneous erasing block are connected to thesource line SL2 in common.

A high voltage Vpp used for erasing is supplied to the source lines SL1and SL2 from voltage output circuits VOUT1 and VOUT2. Output operationsof the voltage output circuits VOUT1 and VOUT2 are selected by an erasecontrol section ECONT.

The word lines WLO to WLn are selected by decoding an X address signalAX captured through an X address latch XALAT by an X address decoderXADEC. A word driver WDRV drives a word line in accordance with theselection signal output of the X address decoder XADEC. For a data readoperation, the word driver WDRV is operated by using a voltage Vcc, suchas 5 V, supplied from a voltage selection circuit VSEL and a groundvoltage, such as 0 V, as its power supply, to drive a word line to beselected at a selection level by the voltage Vcc and to keep a word linenot to be selected at a non-selection level, such as the ground voltage.For a data write operation, the word driver WDRV is operated by using avoltage Vpp, such as 12 V, supplied from the voltage selection circuitVSEL and a ground voltage, such as 0 V, as its power supply, to drive aword line to be selected at a writing high voltage level such as 12 V.For a data erase operation, the output of the word driver WDRV is set ata low voltage level, such as 0 V.

In the case of each of the memory arrays ARY0 to ARY7, the data linesDLO to DLn are connected in common through Y selection switches YSO toYSn. Switching control by the Y selection switches YSO to YSn isperformed by decoding a Y address signal AY captured through a Y addresslatch YALAT by a Y address decoder YADEC. The output selection signalsof the Y address decoder YADEC are supplied to all the memory arraysARY0 to ARY7 in common. Therefore, because one of the output selectionsignals of the Y address decoder YADEC is brought to a selected level,one data line is connected to a common data line CD in each of thememory arrays ARY0 to ARY7.

The data read out of the memory cells MC through the Y selectionswitches is supplied to the sense amplifier SA through a selectionswitch RS and is amplified by the sense amplifier SA and output. Theselection switch RS is set at a selection level synchronously with theread operation. The write data supplied from an external unit is held ina data input latch DIL. When the data held in the data input latch DILis "0", a write circuit WR supplies a writing high voltage through aselection switch WS. The writing high voltage is supplied through a dataline selected by the Y address signal AY to the drain of a memory cellto whose control gate a high voltage is applied, and, thereby, data iswritten in the memory cell. The selection switch WS is set at aselection level synchronously with the write operation. Various timingsfor writing and erasing and voltage selection control are generated by awrite erase control circuit WECONT. Symbol φREAD denotes the switchcontrol signal of the switch RS, φDIL denotes the latch control signalof the data latch DL, and φSA denotes the activation control signal ofthe sense amplifier SA, and these signals are included in the controlsignal 22. Symbol φWRITE denotes the switch control signal of the switchWS.

FIG. 15 is a block diagram of a flash memory 1B representing a thirdembodiment of the present invention. The flash memory shown in FIG. 15is for a semiconductor substrate made of, for example, single-crystalsilicon using a semiconductor integrated circuit fabrication technique.The flash memory 1B of this embodiment is provided with two memoryblocks 2 and 3 in each of which electrically erasable nonvolatile memorycells are arranged in the form of a matrix. The memory blocks 2 and 3each have a memory cell array in which flash memory cells eachcomprising a two-layer insulating-gate field effect transistor arearranged in a matrix configuration, an address decoder for selecting aflash memory cell, and a selection switch circuit. Data is written intoor read from the memory blocks 2 and 3 in units of 8 bits (1 byte) inthe case of this embodiment. Data is input to or output from the memoryblocks 2 and 3 by input/output circuits 4 and 5 in units of one byte.Either of the input/output circuits 4 and 5 may be connected to a datainput/output buffer 7 through the selector 6. The data input/outputbuffer 7 is connected to an external data input/output terminal 8 totransfer data to and from an external unit. The address signals A0 toA20 for selecting memory cells are supplied to the memory blocks 2 and 3from an external address input terminal 9 through an address inputbuffer 10. The address input buffer 10 functions as an address latchcircuit and holds a write address as it is so that the write address canbe used as a write verify address. In this case, the address signals A0to A20 are used for byte addresses. The least significant bit A0 isregarded as information representing which of the memory blocks 2 or 3is designated. In the case of this embodiment, the memory blocks 2 and 3each have a memory capacity of 1M bytes.

In FIG. 15, symbols 43, 44, 45, and 46 denote circuit blocks forcontrolling rewrite or read of information for memory cells of thememory blocks 2 and 3 in accordance with an instruction from an externalunit. Symbol 43 denotes an erase circuit exclusively used for the memoryblock 2. Symbol 44 denotes an erase circuit exclusively used for thememory block 3. Symbol 45 denotes a write circuit used for the memoryblocks 2 and 3 in common. Symbol 46 denotes a timing controller forcontrolling the whole flash memory. The timing controller 46 isconnected to the erase circuits 43 and 44 and the write circuit 45through a signal line group 47.

The erase circuit 43 comprises an erase control circuit 430, an eraseverify control circuit 431 and an erase verify decision circuit 432.Moreover, the erase circuit 44 comprises an erase control circuit 440,an erase verify control circuit 441 and an erase verify decision circuit442. The write circuit 45 comprises a write control circuit 450, a writeverify control circuit 451 and a write verify decision circuit 452.

The timing controller 46 receives output enable signal MOE, write enablesignal MWE and chip enable signal MCE, typically shown as externalaccess control signals. The timing controller 46 has a command register15 to which a command supplied from an external unit through the datainput/output buffer 7 is set to generate internal control signalscorresponding to an operation mode, such as erase, erase verify, write,write verify, or data read, by decoding the command. Symbol 460 denotesa logic circuit for generating the internal control signals by decodingthe command. The signals MOE, MCE, and MWE are supplied to the logiccircuit 460. Though the invention is not so restricted, the controlsignal MWE is provided for ordering the writing of a command into thecommand register. The control signal MOE is provided for ordering a readoperation. The control signal MCE is provided for ordering chipselection.

The erase operation can be performed for every block, for example, every512 bytes. Designation of a block to be erased, though the invention isnot so restricted, is performed in accordance with 12-bit addresssignals A9 to A20. That is, when an erase command is written in thecommand register 15, the address information of an erase start blockspecified by the address signals A9 to A20 (actually, one of internalcomplementary address signals having the same logical value) is set inan erase start block designation register 16S and the addressinformation of an erase end block specified by the address signals A9 toA20 is set in an erase end block designation register 16E. Symbol 16Cdenotes a counter in which the address signals A9 to A20 set in theerase start block designation register 16S is preset. Until the value ofthe counter coincides with the address signal set in the erase block endregister, the counter is incremented at each erase operation. The timingcontroller 46 successively supplies control signals for designatingthe-erase and verify operations to the erase circuits 43 and 44,starting with the erase start block set in the register 16S to the eraseend block set in the register 16E. Particularly, in the case of thisembodiment, A0 is used as the least significant bit of an address signalfor defining a memory space and the least significant bit is used as asignal for separating the memory blocks 2 and 3 from each other.Therefore, the storage region of 512 bytes erased at a time extends overboth the memory blocks 2 and 3. In this case, the erase circuits 43 and44 are exclusively used for the memory blocks 2 and 3. Therefore, in thecase of this embodiment, the erase operation for each block is performedin both of the memory blocks 2 and 3 in parallel. However, this eraseoperation is performed only in the case of a complete compositeconforming circuit.

When a write command is set in the command register 15, the timingcontroller 46 supplies a control signal for writing the write datasupplied through the data input/output buffer 7 into memory cellsdesignated by, for example, the address signals A0 to A20 to the writecircuit 45. The write operation, though the invention is not sorestricted, is performed in units of one byte and the writing of bytedata is performed in either of the memory blocks designated by theaddress signals A0 to A20.

In the case of this embodiment, the least significant address signal A0,as described above, is regarded as a signal representing which isselected, the memory block 2 or 3, in accordance with the logical valueof the signal A0. For example, if A0=0, the memory block 2 is selected;if A0=1, the memory block 3 is selected. In the case of this embodiment,selection of a memory block by A0 means the selection of a memory cellby an address decoder included in the memory block 2 or 3. Therefore,when A0 included in an address signal is 0, memory cells included in thememory block 2 are regarded as access objects. When A0 is 1, memorycells included in the memory block 3 are regarded as access objects.

Symbols a0, a0* to a20, and a20* denote the internal complementaryaddress signals of the address signals A0 to A20. Reference numeral 22denotes a control signal for the input/output circuit 4, referencenumeral 23 denotes a control signal for the input/output circuit 5, andreference numeral 24 denotes a control signal for the selection circuit6.

The flash memory of this embodiment is used as a partial product wheneither of the memory blocks 2 and 3 has an irremediable defect. Theflash memory of this embodiment is provided with a fuse program circuit47 in order to make two partial products completely compatible with acomplete composite conforming circuit, and, moreover, the timingcontroller 46 is provided with an inhibit condition decision circuit 48.

Though the invention is not so restricted, the fuse program circuit 47has a fuse circuit 470 for outputting a signal PSL to be set at lowlevel by the blowing of a fuse and representing that the flash memory isa partial product, a fuse circuit 471 for outputting a signal DE1 to beset at a low level by the blowing of a fuse and representing that thememory block 2 has an irremediable defect, and a fuse circuit 472 foroutputting a signal DE2 to be set at a low level by the blowing of afuse and representing that the memory block 3 has an irremediabledefect. The signals PSL, DE1, and DE2 are supplied to the inhibitcondition decision circuit 48 and the logic circuit 460. The inhibitcondition decision circuit 48 and the logic circuit 460 inhibit theerase, write, and read operations for an irremediable memory block inaccordance with the signals DE1 and DE2, only when the signal PSLindicates that the flash memory is a partial product. The inhibitcondition decision circuit 48 is an example of the detection means fordetecting access to a defective memory block designated by the fuseprogram circuit 47 in accordance with an address signal.

The logic circuit 460 brings a ready/busy signal F,/B to a ready stateand outputs it to an external unit when inhibiting the erase or writeoperation of the memory block. The ready-state ready/busy signal MR/B isused as a status signal representing the completion of the rewriteoperation.

FIG. 16 shows a circuit for inhibiting the output operation of the datainput/output buffer 47 in accordance with the set state of the fuseprogram circuit 47. In FIG. 16, reference numeral 461A denotes an outputcontrol logic circuit and reference numeral 461B denotes an AND gatewhich is included in the logic circuit 460. When the data read mode isset up in accordance with a command, the output control logic circuit461A generates a timing signal 461C for outputting the read datasupplied from a memory cell to an external unit. The AND gate 461Breceives two signals, the timing signal 461C and an inhibit signal 33B,supplied from the inhibit condition decision circuit 48 to control theoutput operation of the data input/output buffer 7 by means of itsoutput.

The inhibit condition decision circuit 48, as shown in FIG. 21,comprises exclusive OR circuits 480 and 481, an OR circuit 482, and aninverter 483. When the flash memory is not a partial product (PSL=1),the inhibit signal 33B is normally set at an inactivation level (highlevel). Therefore, the output operation of the data input/output buffer7 is not inhibited at all. When the flash memory is a partial product(PSL=0), if the fuse of the fuse circuit 471 is blown and the signal DE1is set at 0 (in this case, it is a matter of course that DE2 is set at1), and when the memory block 2 is irremediable, the inhibit signal 33Bis set at an activation level (low level) when a0=0 (access to thememory block 2), while the signal 33B is set at an inactivating level(low level) when a0=1 (access to the memory block 3). Moreover, when theflash memory is a partial product (PSL=0) and the memory block 3 isirremediable, and when the fuse of the fuse circuit •472 is blown andthe signal DE2 is set at 0 (in this case, it is a matter of course thatDE1 is set at 1), the inhibit signal 33B is set at an activation level(low level) when a0=1 (access to the memory block 3), while the signal33B is set at an inactivating level (low level) when a0=0 (access to thememory block 2).

Therefore, even if the read operation access to the memory block 2 isordered (a0=0) when the flash memory is a partial product (PSL=0) inwhich the memory block 2 is defective (DE1=0), the output operation ofthe data input/output buffer 7 is inhibited. Similarly, even if the readoperation access to the memory block 3 is ordered (a0=1) when the flashmemory is a partial product (PSL=0) in which the memory block 3 is adefective (DE2=0), the output operation of the data input/output buffer7 is inhibited.

FIG. 17 shows a circuit for inhibiting operation of the erase controlcircuits 430 and 440 in accordance with the set state of the fuseprogram circuit 47. In FIG. 17, reference numeral 462A denotes an erasestart control logic circuit, and reference numerals 462B and 462C denoteAND gates which are included in the logic circuit 460. When the erasemode is set up by a command, the erase start control logic circuit 462Agenerates an erase-operation start timing signal 462D. The AND gate 462Breceives two signals, the timing signal 462D and the signal DE1, toinhibit the start of the erase control circuit 430 assigned to thememory block 2 when the memory block 2 is defective (DE1=0). The ANDgate 462C receives two signals, the timing signal 462D and the signalDE2, to inhibit the start of the erase control circuit 440 assigned tothe memory block 3 when the memory block 3 is defective.

FIG. 18 shows a circuit for inhibiting the operation of the erase verifycontrol circuits 431 and 441 in accordance with the set state of thefuse program circuit 47. In FIG. 18, reference numeral 463A denotes anerase verify start control circuit and reference numerals 463B, 463C and463D denote AND gates which are included in the logic circuit 460. Whenthe erase mode is set up in accordance with a command, the erase verifystart control logic circuit 462A generates a start timing signal 463Efor the erase verify operation. When the erase verify operation isstarted, the erase verify control circuit 431 (441) instructs the eraseblock of the corresponding memory block 2 (3) to read data in units ofone byte. The read data is supplied to the erase verify decision circuit432 (442) and it is judged whether the data is used as the logical valuein an erase state. As shown in FIG. 22, it is possible to constitute theerase verify decision circuit 432 (442) with a logic circuit equivalentto an eight-input NAND gate. The erase verify decision circuit 432 (442)inverts the logical value of an output signal 432A (442A) from "1" to"0" by detecting that all memory cells of a block to be erased arebrought into an erase state.

The AND gate 463B receives three signals 463E, DE1, and 432A to inhibitthe start of operation of the erase verify control circuit 431 assignedto the memory block 2 when the memory block 2 is defective (DE1=0). Thatis, the output state of the AND gate 463B is kept in the completed erasestate (logical value "0" is output). The AND gate 463C receives threesignals 463E, DE2, and 442A to inhibit the start of the erase verifycontrol circuit 431 assigned to the memory block 3 when the memory block3 is defective (DE1=0). That is, the output state of the AND gate 463Cis kept in the completed erase state (logical value "0" is output). TheAND gate 463D receives two signals output from the erase verify controlcircuits 431 and 441 when the erasing of the data in all blocks to beerased is completed. The output of the AND gate 463D is supplied to anOR gate 466. The OR gate 466 is a circuit equivalent to a circuitcomprising the busy status generator 140, transistor 36, and resistor 35described with reference to FIG. 4. The OR gate 466 outputs theready/busy signal MR/B.

FIG. 19 shows a circuit for inhibiting the operation of the writecontrol circuit 450 in accordance with the set state of the fuse programcircuit 47. In FIG. 19, reference numeral 464A denotes a write startcontrol circuit and reference numeral 464B denotes an AND gate, andthese circuits are included in the logic circuit 460. When the writemode is set up in accordance with a command, the write start controlcircuit 464A generates a timing signal 464C for starting the writeoperation of a memory cell. The AND gate 464B receives two signals, thetiming signal 464C and the inhibit signal 33B, sent from the inhibitcondition decision circuit 48 to control the start of the writeoperation of the write control circuit 450 by means of its output.

The inhibit condition decision circuit 48 is constituted as describedabove. Therefore, when a partial product is used (PSL=0) in which thememory block 2 is defective (DE=0), even if memory cells of the memoryblock 2 are designated as a write object when a0=0, the start of thewrite control circuit 450 is inhibited. Similarly, when a partialproduct is used (PSL=0) in which the memory block 3 is defective (DE=1),even if memory cells of the memory block 3 are designated as a writeobject when a0=1, the start of the write control circuit 450 isinhibited.

FIG. 20 shows a circuit for selectively inhibiting the operation of thewrite verify control circuit 451 in accordance with the set state of thefuse program circuit 450. In FIG. 20, symbol 465A denotes a write verifystart control logic circuit and 465B denotes an AND gate, and thesecircuits are included in the timing controller 46. When the data writemode is set up in accordance with a command, the write verify startcontrol logic circuit 465A generates a timing signal 465C for startingthe write verify operation. When the write verify operation is started,the write verify control circuit 451 reads data from a write operatedaddress. The read data is supplied to the write verify decision circuit452 and tit is judged whether or not the data coincides with the logicalvalue of write data. As shown in FIG. 23, it is possible to constitutethe write verify decision circuit 452 with an exclusive OR circuit andan OR gate which compare the write data supplied from an external unitwith the data read out of memory cells after being written in abit-correspondence way.

The write verify decision circuit 452 inverts the logical value of averify decision signal 452A from "1" to "0" by detecting the coincidentstate of write data with read data (completed write state).

The AND gate 465B receives three signals, the verify decision signal452A, the inhibit signal 33B and the start signal 465C, to inhibit thestart of operation of the write verify control circuit 451, similar tothe case of the write control circuit 450, even if memory cells of thememory block 2 are designated as a write object when a0=0, when theflash memory is a partial product (PSL=0) in which the memory block 2 isdefective (DE=0). That is, the output state of the AND gate 465B is keptin the completed write state (logical value "0" is output) by thelow-level inhibit signal 33B. Moreover, the AND gate 465B inhibits thestart of operation of the write verify control circuit 451, similar tothe case of the write control circuit 450, even if memory cells of thememory block 3 are designated as a write object when a0=1, when theflash memory is a partial product (PLS=0) in which the memory block 3 isdefective (DE=1). That is, the output state of the AND gate 465B is keptin the completed write state (logical value "0" is output) by thelow-level inhibit signal 33B.

This embodiment is also provided with the fuse program circuit 34capable of inverting the logical value of the address signal A0similarly to the case of FIG. 1.

FIG. 24 schematically shows the fabrication process of the flash memoryshown in FIG. 15. The flash memory is passed through the wafer process(Sp1) for forming various circuits described with reference to FIG. 15on a wafer, such as a single-crystal silicon substrate, and, thereafter,undergoes device tests including a function test (Sp2). Thereby, flashmemory chips are sorted into complete composite conforming circuits,high-order partial products (only the memory block 3 has an irremediabledefect), low-order partial products (only the memory block 2 has anirremediable defect), and defective products. Moreover, the fuse programcircuit is provided depending on the sort result (Sp3). In theembodiment in FIG. 15, PSL is set at 1, DE1 is set at 1, and DE2 is setat 1 in the case of a complete composite conforming circuit; PSL is setat 0, DE1 is set at 1, and DE2 is set at 0 in the case of a low-orderpartial product; and PSL is set at 0, DE1 is set at 0, and DE2 is set at1 in the case of a high-order partial product. The set state of acomplete composite conforming circuit corresponds to the initial stateof a fuse program circuit. Thereafter, each flash memory chip is sealedin a package depending on the sorted state (Sp4) and undergoes a sortingtest after being sealed (Sp5), and thus it is completed. Chips ofcomplete composite conforming circuits are sealed one by one. In thecase of partial product chips, a high-order partial product and alow-order partial product are paired and sealed as, for example, thememory device described with reference to FIGS. 3(A) and 4. When thereis a difference between the number of high-order partial products andthe number of low-order partial products, it is possible to cope withthe fact in a way similar to the above by changing the state of the fuseprogram circuit 34 for part of the larger number of chips.

FIGS. 25(A) to 25(C) relates to a procedure for effecting the eraseoperation of a complete composite conforming circuit of the flash memory1B shown in FIG. 15. In the address map of the flash memory shown inFIG. 25(A), symbols #0, #1, . . . denote byte addresses. In the case ofthe flash memory 1B in FIG. 15, the least significant address bit A0 isregarded as memory block selecting information. Therefore, an eraseblock of 512 bytes extends over both the memory blocks 2 and 3. The setstate of the fuse program circuit 47 of a complete composite conformingcircuit is as described above.

As shown in FIG. 25(C), the flash memory is brought into a commandwaiting state after the power supply is turned on (Se1). Commands, asshown in Se2 to Se4, are set by dividing them into a first command, asecond command, and a third command. The first command is a command fordesignating an erase start block, and the erase start block is set inthe register 16S as address information A9 to A20. For example, theerase block 1 shown in FIG. 25(A) is designated as the erase startblock. The second command is a command for designating an erase endblock, and the erase end block is set in the register 16E as addressinformation A9 to A20. For example, the erase block 3 shown in FIG.25(A) is designated as the erase end block. The third command is acommand for ordering the erase operation and set in the register 15.When the setting of the above commands is completed, the erase operationof the erase block 1 is started (Se5). The erase operation of the memoryblocks 2 and 3 is performed in parallel. That is, the simultaneous eraseoperation (Se6) for 256 bytes constituting the erase block 1 in thememory block 2 (also referred to as low-order memory block 2) and thesimultaneous erase operation (Se7) for 256 bytes constituting the eraseblock 1 in the memory block 3 (also referred to as high-order memoryblock 3) are performed in parallel and the erase verify operation isperformed for each erase operation (Se8 and Se9). By confirming that allmemory cells of a block to be erased are brought into an erased statethrough an erase verify operation, the erase operation of one eraseblock is ended. When there is a memory cell which cannot be finallybrought into an erased state, the erase operation is regarded asabnormally ended (Se10). When the erase operation for one erase block isnormally ended, the counter 16C is incremented to increment the blocknumber to be erased (erase block No.) to the next block number (Se11)and judges whether or not the erase block number is smaller than theblock number of the erase end block (Se12). When the former is smallerthan the latter, the processing of the next erase block is carried outfrom the above step Se5. Then the former is not smaller than the latter,the internal processing for erasing is ended (Se13).

FIGS. 26(A) to 26(C) relate to a procedure for effecting the eraseoperation of the low-order partial product of the flash memory 1B shownin FIG. 15. The set state of the fuse program circuit 47 of thelow-order partial product is as described above. In this case, becausethe high-order memory block 3 is defective, as shown in FIG. 26(B), thebyte addresses of the defective portions are alternately arranged asshown by the address map of FIG. 26(A). This is because the leastsignificant address bit A0 of the flash memory of FIG. 15 is regarded asmemory block selecting information.

In the case of the erase operation procedure shown in FIG. 26(C), theprocessings at steps Se7 and Se9 are different from those of FIG. 25(C),in which the erase operation and verify operation of the high-ordermemory block 3 are inhibited. That is, as described with reference toFIGS. 17 and 18, the signal DE2 output from the fuse program circuit 47is set at a low level with the result that these processings areinhibited.

FIGS. 27(A) to 27(C) relate to a procedure for implementing the eraseoperation for the high-order partial product of the flash memory 1Bshown in FIG. 15. The set state of the fuse program circuit 47 of thehigh-order partial product is as described above. In this case, becausethe low-order memory block 2 is defective, as shown in FIG. 27(B), thebyte addresses of the defective portions are alternately arranged asshown by the address map of FIG. 27(A).

In the case of the erase operation procedure shown in FIG. 27(C), theprocessings at steps Se6 and Se8 are different from those of FIG. 25(C),in which the erase operation and erase verify operation for thelow-order memory block 2 are inhibited. That is, as described withreference to FIGS. 17 and 18, the signal DE1 output from the fuseprogram circuit 47 is set at a low level with the result that theseprocessings are inhibited.

FIGS. 28(A) to 28(C) relate to a procedure for effecting a writeoperation for the complete composite conforming circuit of the flashmemory 1B shown in FIG. 15. In the address map of the flash memory shownin FIG. 28(A), symbols #0, #1, . . . denote byte addresses.

As shown in FIG. 28(C), the flash memory is brought into a commandwaiting state (Sw1) after the power supply is turned on. Commands, asshown by Sw2 and Sw3, are commands for ordering the write operation landwrite data. The write command is set in the register 15 (Sw2) and thewrite data is supplied together with write addresses (Sw3). The writedata is supplied to the data input/output buffer 7 and the writeaddresses (A0 to A20) are supplied to the address buffer 10. Moreover,the operation of writing the write data in designated write addresses isstarted (Sw4) and the verify operation is performed (Sw5) after thewrite operation is completed. The write operation is ended by confirmingthat the data is normally written through a write verify operation(Sw6).

FIGS. 29(A) to 29(C) relate to a procedure for effecting a writeoperation for the low-order partial product of the flash memory 1B shownin FIG. 15. The set state of the fuse program circuit 47 of thelow-order partial product is as described above. In this case, becausethe high-order memory block 3 is defective as shown in FIG. 29(B), thebyte addresses of the defective portions are alternately arranged asshown on the address map of FIG. 29(A).

In the case of the write operation shown in FIG. 29(C), processings atand after step Sw3 are different from those of FIG. 28(C), in which thewrite operation e,nd the write verify operation for the high-ordermemory block 3 are inhibited (Sw41 and Sw51). That is, as described withreference to FIGS. 19 and 20, the signals SPL and DE2 output from thefuse program circuit 47 are set at low levels and the inhibit signal 33Bis set at low level when A0=1 (a0=1). Therefore, these processings areinhibited. The write operation and the write verify operation areperformed for the low-order memory block 3 (Sw42 and Sw52).

FIGS. 30(A) to 30(C) relate to a procedure for effecting a writeoperation for the high-order partial product of the flash memory 1Bshown in FIG. 15. The set state of the fuse program circuit 47 of thehigh-order partial product is as described above. In this case, becausethe high-order memory block 2 is defective, as shown in FIG. 30(B), thebyte addresses of the defective portions are alternately arranged asshown on the address map of FIG. 30(A).

In the case of the write operation procedure shown in FIG. 30(C),because the low-order memory block 2 is a defective memory block, thewrite operation and the write verify operation for the low-order memoryblock 2 are inhibited (Sw41 and Sw51). That is, as described withreference to FIGS. 19 and 20, the signals SPL and DE1 output from thefuse program circuit 47 are set at low levels and the inhibit signal 33Bis set at low level when A0=0 (a0=0). Therefore, these processings areinhibited. The write operation and the write verify operation areperformed for the high-order memory block 3 (Sw42 and Sw52).

FIG. 31 shows a block diagram of a flash memory 1C representing a fourthembodiment of the present invention. The flash memory shown in FIG. 31is formed on a semiconductor substrate made of, for example,single-crystal silicon using a semiconductor integrated circuitfabrication technique. The flash memory 1C of this embodiment isprovided with two memory blocks 2Y and 3Y in each of which electricallyerasable nonvolatile memory cells are arranged in the form of a matrix.The memory blocks 2Y and 3Y each have a memory cell array in which flashmemory cells constituting the two-layer insulating-gate field effecttransistor are arranged in a matrix configuration, an address decoderfor selecting a flash memory cell, and a selection switch circuit. Inthe case of this embodiment, data is written in or read from the memoryblocks 2Y and 3Y in units of 8 bits (one byte). Data is input to oroutput from the memory blocks 2Y and 3Y by input/output circuits 4 and 5in units of one byte. Either of the input/output circuits 4 and 5 isconnected to a data input/output buffer 7 through a selector 6. The datainput/output buffer 7 is connected to an 8-bit external datainput/output terminal 8 to transfer data to and from an external unit.Address signals A0 to A20 for selecting memory cells are supplied to thememory blocks 2Y and 3Y from external address input terminals 9 throughan address input buffer 10. The address input buffer 10 functions as anaddress latch circuit and holds, for example, a write address as it isso that the write address can be used as a write verify address. In thiscase, the address signals A0 to A20 are byte addresses, and,particularly, the most significant bit A20 is regarded as informationrepresenting which memory block is designated, 2Y or 3Y. In the case ofthis embodiment, the memory blocks 2Y and 3Y each have a memory capacityof 1M bytes.

In FIG. 31, symbols 43Y, 45, and 46Y denote circuit blocks forcontrolling the rewrite and read of information for the memory cells ofthe memory blocks 2 and 3 in accordance with an instruction from anexternal unit. Symbol 43Y denotes a circuit shared by the memory blocks2Y and 3Y. Symbol 45 denotes a write circuit, which is the same as thatof the third embodiment. Symbol 46Y denotes a timing controller forcontrolling the whole of the flash memory. The timing controller 46Y isconnected to the erase circuit 43Y and the write circuit 45 through asignal line group.

The erase circuit 43Y comprises an erase control circuit 430Y, an eraseverify control circuit 431Y and an erase verify decision circuit 432Y.

The timing controller 46Y receives an output enable signal MOE, a writeenable signal MWE, and a chip enable signal MCE, typically shown asexternal access control signals. The timing controller 46Y has a commandregister 15 in which a command supplied from an external unit throughthe data input/output buffer 7 is set and generates an internal controlsignal corresponding to an operation mode, such as erase, erase verify,write, write verify, or data read, by decoding the command. Symbol 460Ydenotes a logic circuit for generating the internal control signal bydecoding the command. The signals MOE, MCE, and MWE are supplied to thelogic circuit 460Y. Though the invention is not so restricted, thecontrol signal MWE orders the write of a command into the commandregister. The control signal MOE orders a read operation. The controlsignal MCE gives an instruction for chip selection.

The erase operation can be performed for every block, for example, every512 bytes. Designation of a block to be erased, though the invention isnot so restricted, is performed in accordance with 11-bit addresssignals A10 to A20. That is, when an erase command is written into thecommand register 15, the address information of an erase start blockspecified by the address signals A10 to A20 is set in an erase startblock designation register 16S and the address information of an eraseend block specified by the address signals A10 to A20 is set in an eraseend block designation register 16E. Symbol 16C denotes a counter inwhich the address signals A10 to A20 set in the erase start blockdesignation register 16S are preset, and the counter is incremented ateach erase operation until the value of the counter coincides with anaddress signal set in the erase block end register. The timingcontroller 46Y successively supplies control signals for designating theerase operation and the verify operation to the erase circuit 43Y,starting with the erase start block set in the register 16S to the eraseend block set in the register 16E. Particularly, in the case of thisembodiment, A20 is regarded as the most significant bit of an addresssignal for defining a memory space and the most significant bit servesas a signal for separating the memory blocks 2Y and 3Y from each other.Therefore, the memory region of 512 bytes, i.e., a simultaneous eraseunit, does not extend over both the memory blocks 2Y and 3Y. In thiscase, the erase circuit 43 is shared by the memory blocks 2Y and 3Y.Therefore, in the case of this embodiment, the erase operation of adesignated block is performed by either of the memory blocks 2Y and 3Y.

When a write command is set in the command register 15, the timingcontroller 46Y supplies a control signal for writing the write datasupplied through the data input/output buffer 7 into memory cellsdesignated by the address signals A0 to A20. The write operation, thoughthe invention is not so restricted, is performed in units of one byteand the writing of byte data is performed by either of the memoryblocks, designated by the address signals A0 to A20.

In the case of this embodiment, the most significant address signal A20,as described above, is regarded as a signal representing which memoryblock is selected, 2Y or 3Y, in accordance with the logical value of thesignal 20A. For example, the memory block 2Y is selected when A20=0 andthe memory block 3Y is selected when A20=1. In the case of thisembodiment, the selection of a memory block in accordance with A20refers to the selection of a memory cell by the address decoder includedin the memory block 2Y or 3Y. Therefore, when A20 included tin anaddress signal is 0, a memory cell included in the memory block 2Y is anobject to be accessed. When A20 is 1, a memory cell included in thememory block 3Y is an object to be accessed.

Symbols a0, a0* to a20, and a20* denote the internal complementaryaddress signals of the address signals A0 to A20. Reference numeral 22denotes a control signal for an input/output circuit 4, referencenumeral 23 denotes a control signal for an input/output circuit 5, andreference numeral 24 denotes a control signal for a selection circuit 6.

The flash memory 1C of this embodiment is a partial product when eitherof the memory blocks 2Y and 3Y has an irremediable defect. The flashmemory 1C of this embodiment is provided with a fuse program circuit 47in order to make two partial products completely compatible with acomplete composite conforming circuit and moreover, the timingcontroller 46Y is provided with an inhibit condition decision circuit48Y.

The fuse program circuit 47 has a fuse circuit 470 for outputting asignal PSL, a fuse circuit 471 for outputting a signal DE1, and a fusecircuit 472 for outputting a signal DE2. The signals PSL, DE1, and DE2are supplied to the inhibit condition decision circuit 48Y and the logiccircuit 460Y. The inhibit condition decision circuit 48Y and the logiccircuit 160Y inhibit operations, such as erase, write, or read, for anirremediable memory block in accordance with the signals DE1 and DE2,only when the signal PSL represents that the flash memory is a partialproduct. The inhibit condition decision circuit 48Y realizessubstantially the same function as that of the inhibit conditiondecision circuit 48 of the third embodiment. When the logic circuit 460Yinhibits the erase or write operation of the memory block, it brings aready/busy signal MR/B into a ready state and outputs the signal to anexternal unit. In FIG. 31, the same circuit blocks and signals as thosedescribed in the third embodiment are denoted by the same symbols.

FIG. 32 shows a circuit for inhibiting the output operation of the datainput/output buffer 7 in accordance with the set state of the fuseprogram circuit 47. In FIG. 32, reference numeral 461A denotes an outputcontrol circuit and reference numeral 461B denotes an AND gate, whichare included in the logic circuit 460Y. When the data read mode is setup in accordance with a command, the output control circuit 461Agenerates a timing signal 461C for outputting the data read from amemory cell to an external unit. The AND gate 461B receives two signals,the timing signal 461C and the inhibit signal 33B, supplied from theinhibit condition decision circuit 48Y, to control the output operationof the data input/output buffer 7 by means of the output of the gate461B.

The inhibit condition decision circuit 48Y can have the same logicalstructure as that of the circuit illustrated in FIG. 21. However, a20 issupplied instead of a0. When the flash memory is a partial product(PSL=1), the inhibit signal 33B is normally set at an inactivation level(high level). Therefore, the output operation of the data input/outputbuffer 7 is not inhibited at all. When the flash memory is a partialproduct (PSL=0), if the memory block 2Y is irremediable, the fuse of thefuse circuit 471 is blown, and the signal DE1 is set at 0 (in this case,it is a matter of course that the DE2 is set at 1), the inhibit signal33B is set at an activation level (low level) when a20=0, while thesignal 3B is set at an inactivation level (low level) when a20=1 (accessto the memory block 3Y). Similarly, when the flash memory is a partialproduct (PSL=0), if the memory block 3Y is irremediable and the signalDE2 is set at 0 (in this case, it is a matter of course that DE1 is setat 1), the inhibit signal 33B is set at an activation level (low level)when a20=1 (access to the memory block 3Y) while the signal 33B is setat an inactivation level (low level) when a20=0 (access to the memoryblock 2Y).

Therefore, in the case of a partial product (PSL=0) in which the memoryblock 2Y is defective (DE1=0), even if a read operation access to thememory block 2Y is designated (a20=0), the output operation of the datainput/output buffer 7 is inhibited. Similarly, in the case of a partialproduct (PSL=0) in which the memory block 3Y is defective (DE2=0), evenif a read operation access to the memory block 3Y is designated (a20=1),the output operation of the data input/output buffer 7 is inhibited.

FIG. 33 shows a circuit for inhibiting operation of the erase controlcircuit 430Y in accordance with the set state of the fuse programcircuit 47. In FIG. 33, symbol 462A denotes an erase start control logiccircuit and 462E denotes an AND gate, and they are included in the logiccircuit 460Y. When the erase mode is set up in accordance with acommand, the erase start control logic circuit 462A generates an eraseoperation start timing signal 462F. The AND gate 462E receives thetiming signal 462F and the inhibit signal 33B.

Thereby, for a partial product (PSL=0) in which the memory block 2Y isdefective (DE1=0), even if the erase operation start signal 462F isactivated, the start of the erase control circuit 430Y is inhibited bythe inhibit signal 33B in the case of the erase operation for the memoryblock 2Y (a20=0). Similarly, for a partial product (PSL=0) in which thememory block 3Y is defective (DE2=1), even if the erase operation startsignal 462F is activated, the start of the erase control circuit 430Y isinhibited by the inhibit signal 33B in the case of the erase operationfor the memory block 3Y (a20=1).

FIG. 34 shows a circuit for inhibiting the operation of the erase verifycontrol circuit 431Y in accordance with the set state of the fuseprogram circuit 47. In FIG. 34, reference numeral 463A denotes an eraseverify start control logic circuit and reference numeral 463G denotes anAND gate, and they are included in a timing controller 46M. When theerase mode is set up in accordance with a command, the erase verifystart control logic circuit 462A generates a start timing signal 463E.When the erase verify operation is started, the erase verify controlcircuit 431Y reads data from a block to be erased from the memory block2Y or 3Y in units of one byte. The read data is supplied to the eraseverify decision circuit 432Y and it is judged whether or not the data isset at a logical value in an erased state. As shown in FIG. 22, it ispossible to constitute the erase verify decision circuit 432Y with alogic circuit equivalent to an 8-input NAND gate. When the erase verifydecision circuit 432Y detects that all memory cells of a block to beerased are brought into an erased state, it converts the logical valueof the output signal 432A from The AND gate 463G receives three signals463E, 33B and 432A, to inhibit the start of the erase verify controlcircuit 431Y because a20=0, which is regarded as the designation of thememory block 2Y when the memory block 2Y is defective (PSL=0 and ED1=0).That is, the output state of the AND gate 463B is kept in the completederase state (logical value "0" is output). When the memory block 3Y isdefective (PSL=0 and DE2=0), the gate 463G inhibits the start of theerase verify control circuit 431Y because a20=0, which is regarded asthe designation of the memory block 2Y. That is, the output state of theAND gate 463G is kept in the completed erase state (logical value "0" isoutput). In FIG. 34, components having the same functions as those ofFIG. 18 are denoted by the same symbols.

FIG. 35 shows a circuit for inhibiting the operation of the writecontrol circuit 450 in accordance with the set state of the fuse programcircuit 47. The circuit has substantially the same circuit structure asthat of FIG. 19 except that the address input of the inhibit conditiondecision circuit 48Y is a20. By using this circuit, even if a memorycell of the memory block 2Y is designated as a write object in the caseof a partial product (PSL=0) in which the memory block 2Y is defective(DE1=0) in accordance with a20=0, the start of the write control circuit450 is inhibited. Similarly, even if a memory cell of the memory block3Y is designated as a write object in accordance with a20=1 in the caseof a partial product (PSL=0) in which the memory block 3Y is defective(DE2=0), the start of the write control circuit 450 is inhibited. InFIG. 35, components having the same functions as those of FIG. 19 aredenoted by the same symbols.

FIG. 36 shows a circuit for selectively inhibiting the operation of thewrite verify control circuit 451 in accordance with the set state of thefuse program circuit 47. The circuit has substantially the samestructure as that of FIG. 20 except that the address input of theinhibit condition decision circuit 48Y is a20. By using this circuit,the AND gate 465B inhibits the start of the write verify control circuit451 similar to the case of the write control circuit 450 even if amemory cell of the memory block 2Y is designated as a write object,according to a20=0 in the case of a partial product (PSL=0) in which thememory block 2Y is defective (DE1=0). That is, the output state of theAND gate 465B is kept in the completed write state (logical value "0" isoutput) in accordance with the low-level inhibit signal 33B. Moreover,the AND gate 465B inhibits the start of the write verify control circuit451 similar to the case of the write control circuit 450 even if amemory cell of the memory block 3Y is designated as a write object inaccordance with a20=1 in the case of a partial product (PLS=0) in whichthe memory block 3Y is defective (DE2=0). That is, the output state ofthe AND gate 465B is kept in the completed write state (logical value"0" is output) in accordance with the low-level inhibit signal 33B.

The flash memories 1C of the fourth embodiment a,re also sorted intocomplete composite conforming circuits, high-order partial products,low-order partial products and defective products through the sameprocess as that described with reference to FIG. 24, and the fuseprogram circuit 47 is set in accordance with the sort results. The setcontents of the fuse program are the same as those described withreference to FIG. 24. A partial product chip is constituted by pairing ahigh-order partial product and a low-order partial product and is sealedas a memory device as described with reference to FIGS. 3 and 4. It ispossible to constitute a memory card described with reference to FIG. 5by using the memory device.

FIGS. 37(A) to 37(C) relates to a procedure for effecting an eraseoperation for the complete composite conforming circuit of the flashmemory 1C shown in FIG. 31. On the address map of the flash memory shownin FIG. 37(A), symbols #0, . . . , and #1048575 denote byte addresses.In the case of the flash memory 1C of FIG. 31, the most significantaddress bit A20 is regarded as information for selecting a memory block.Though the invention is not so restricted, the last byte address of thelow-order memory block 2Y is designated as #1048575 and the first byteaddress of the high-order memory block 3Y is designated as #1048576. Theset state of the fuse program circuit 47 of the complete compositeconforming circuit is as described above.

FIG. 37(C) showing the erase procedure for a complete compositeconfirming circuit is different from FIG. 25(C) with respect to stepsSe14, Se15, and Se16. That is, a simultaneous erase unit block isincluded in either of the memory blocks in accordance with the logicalvalue of A20 regarded as the information for selecting a memory block.Other points are the same as described with reference to FIG. 25.

FIGS. 38(A) to 38(C) relate to a procedure for effecting an eraseoperation for the low-order partial product of the flash memory shown inFIG. 31. The set state of the fuse program circuit 47 of the low-orderpartial product is as described above. In this case, the high-ordermemory block 3Y is defective as shown in FIG. 38(B). In the case of thisexample, the erase block 2048 included in the low-order memory block 2Yand the erase blocks 2049 and 2050 included in the high-order memoryblock 3Y are objects to be continuously erased, as shown on the addressmap of FIG. 38(A).

In the erase operation procedure shown in FIG. 38(C), the blocks to beerased are designated at steps Se2 and Se3. When the erase processing isstarted at step Se5, the erase operation and the erase verify operationfor the erase blocks included in the high-order memory block 3Y areinhibited (Se140, Se141, Se142, Se151, and Se152). That is, as describedwith reference to FIGS. 33 and 34, the signal DE2 output from the fuseprogram circuit 47 is set at a low level and resultingly, theseprocessings are inhibited.

FIGS. 39(A) to 39(C) relate to a procedure for effecting an eraseoperation for the high-order partial product of the flash memory shownin FIG. 31. The set state of the fuse program circuit 47 of thehigh-order partial product is as described above. In this case, thelow-order memory block 2Y is defective as shown in FIG. 39(B). In thecase of this example, the erase block 2048 included in the low-ordermemory block 2Y and the erase blocks 2049 and 2050 included in thehigh-order memory block 3Y are objects to be continuously erased.

In the erase operation procedure shown in FIG. 39(C), the blocks to beerased are designated at steps Se2 and Se3. When the erase processing isstarted at step Se5, the erase operation and the erase verify operationfor the erase blocks included in the low-order memory block 2Y areinhibited (Se140, Se141, Se142, Se151, and Se152). That is, as describedwith reference to FIGS. 33 and 34, the signal DE1 output from the fuseprogram circuit 47 is set at a low level with the result that theseprocessings are inhibited.

FIGS. 40(A) to 40(C) relate to a procedure for effecting a writeoperation for the complete composite conforming circuit of the flashmemory shown in FIG. 31. The write procedure is basically the same asthe procedure of FIG. 18.

FIGS. 41(A) to 41(C) relate to a procedure for effecting a writeoperation for the low-order partial product of the flash memory shown inFIG. 31. The procedure is different from that of FIG. 29(C) in that amemory block is designated by the most significant bit A20 of an addresssignal, and the write operation and the write verify operation for thehigh-order memory block 3Y are inhibited when A20=1 (Sw41 and Sw51).That is, as described with reference to FIGS. 19 and 20, the signals SPLand DE2 output from the fuse program circuit 47 are set at low levels,and the inhibit signal 33B is set at a low level when A20=1 (a20=1). Asa result, these processings are inhibited. The write operation and thewrite verify operation are performed for the low-order memory block 2Y(Sw42 and Sw52).

FIGS. 42(A) to 42(C) relate to a procedure for effecting a writeoperation for the high-order partial product of the flash memory shownin FIG. 31. The procedure is different from that of FIG. 30(C) in that amemory block is designated by the most significant bit A20 of an addresssignal, and the write operation and the write verify operation for thelow-order memory block 2Y are inhibited when A20=0 (Sw41 and Sw51). Thatis, as described with reference to FIGS. 19 and 20, the signals SPL andDE1 output from the fuse program circuit 47 are set at low levels, andthe inhibit signal 33B is set at a low level when A20=0 (a20=0) with theresult that these processings are inhibited. The write operation and thewrite verify operation are performed for the high-order memory block 3Y(Sw42 and Sw52).

From the above embodiments, the following functions and advantages canbe obtained.

For the first, second, and fourth embodiments, when a memory block to beselected in accordance with address information coincides with thememory block (defective memory block in a partial product) designated bythe fuse program circuits 30, 100, and 47, it is possible to inhibit thedata rewrite operation for an instruction for a data rewrite operation(erase and write) by the first control means 11 and 81 or the erasecircuit 43, write circuit 45, and timing controller 46, and, moreover,it is possible to inhibit the output operation of the data input/outputbuffer 7 for an instruction for an information read operation.

For the first to fourth embodiments, when the access to a defectivememory block is detected, it is possible to output a status MR/B signalrepresenting the completion of the data rewrite operation for theinstruction of the data rewrite operation irrespective of the completionof the operation, and, moreover, inhibit the output operation of a datainput/output buffer for an instruction for a data read operation.

It is possible to use a partial product without fixing a specificaddress specifying a memory block outside a semiconductor memory on asystem by the inhibit function of the semiconductor memory itselfserving as the partial product.

Therefore, it is possible to easily constitute a memory device byconnecting the external terminals of the high-order partial product 1-Uwith those of the low-order partial product 1-L in common. Thereby, itis possible to achieve compatibility of the memory crevice 40 with thesemiconductor memory of a complete composite conforming circuit from theviewpoint of external terminal specifications or utilization mode.

Moreover, even if the information rewrite operation for a defectivememory block in a partial product is ordered from an external unit, theinformation rewrite operation for the memory block is inhibited or, asdescribed above, a status signal representing the completion of the datarewrite operation can be output to an external unit irrespective thecompletion of the operation. Therefore, when the operation of thedefective portion of a partial product is ordered in accordance with anaccess from an external unit, it is possible to prevent a contradictionfrom occurring in the internal state between the partial product andanother partial product substituted for the defective portion of theformer partial product.

Defective portions of a plurality of partial products typically aremaldistributed depending on the fabrication process. By using logicmeans for selectively inverting the address information designated toselect a memory block in accordance with the value set in the fuseprogram circuit 34, it is possible to optionally change the arrangementof apparently operable memory blocks for an address signal supplied froman external unit depending on the way the information is set in the fuseprogram circuit 34 even if partial products whose defective portionsdiffer are biased in quantity. Thereby, when substituting anon-defective product by combining partial products whose operationalregions are complementary, it is possible to prevent excess of defectivepartial products of one type, the number of which is larger than theother type.

It is possible to constitute the memory card 50 comprising a partialproduct of a flash memory by using a high-order partial product 1-U anda low-order partial product 1-L, instead of a flash memory which is acomplete composite conforming circuit and mounting the partial productson a wiring board and connecting the external terminals of the partialproducts in common on the wiring board. Because the processing for adefective portion of a flash memory used as a partial product can berealized in the flash memory by programming a fuse program circuit asdescribed above, it is unnecessary to fix the input level of a specificaddress terminal of the flash memory. Moreover, it is possible toprovide the wiring of a mounting substrate and the chip selection logicof a card controller in common even if the flash memory used for amemory card is a partial product or complete composite conformingcircuit.

Therefore, it is possible to realize a favorable compatibility of amemory device or memory card using a partial product with a productusing a complete composite conforming circuit. It is possible to use thepartial product of a semiconductor memory directly in a memory device ormemory card, instead of a complete composite conforming circuit.

The invention made by the present inventor has been specificallydescribed above, taking various embodiments as examples. However, thepresent invention is not restricted to the specific embodiments. It isneedless to say that various modifications of the present invention areallowed as long as they do not depart from the gist of the presentinvention. For example, the number of memory blocks is not restricted totwo. It is possible to use four or eight memory blocks. Moreover, thesemiconductor memory can be used not only in a flash memory, but also inother nonvolatile semiconductor memories and random access memories,such as an EPROM, EEPROM, and mask ROM.

As described above, the present invention can be applied to asemiconductor memory, such as a flash memory, a memory device achievingcompatibility with a non-defective semiconductor memory by combiningsemiconductor memories, such as flash memories, with semiconductormemories having irremediable local defects, and a memory card using thememory device, and they can be applied to memory circuits of computersystems of various sizes.

What is claimed is:
 1. A semiconductor memory comprising:a plurality ofmemory blocks having a plurality of memory cells; a data input/outputbuffer for receiving data written in the memory blocks from an externalunit and for outputting data read out of the memory blocks to anexternal unit; control means for controlling the rewriting and readingof data for the memory cells; storage means for designating defectivememory blocks included in said plurality memory blocks; and detectionmeans for detecting the defective memory blocks designated by saidstorage means in accordance with a received address signal; whereinsaidcontrol means inhibits a data rewrite operation for an instruction for adata rewrite operation when said detection means detects an access to adefective memory block and inhibits a data output operation of said datainput/output buffer for an instruction for a data read operation.
 2. Amemory device comprising a plurality of semiconductor memories asdefined in claim 1, wherein the semiconductor memories are provided in arelation in which one memory is substituted for a defective memory blockof another, and external terminals having the same function areconnected in common in each semiconductor memory.
 3. A semiconductormemory comprising:a plurality of memory blocks having a plurality ofelectrically erasable memory cells; a data input/output buffer forreceiving data written in the memory blocks from an external unit andfor outputting data read out of the memory blocks to an external unit;first control means for controlling the rewriting and reading of datafor the memory cells; first storage means for designating defectivememory blocks included in said plurality of memory blocks; and detectionmeans for detecting the defective memory blocks designated by the firststorage means in accordance with a received address signal; whereinthefirst control means generates a status signal representing thecompletion of a data rewrite operation for an instruction for a datarewrite operation in such a way that the status can be output to anexternal unit irrespective of the completion of the data rewriteoperation when the detection means detects an access to a defectivememory block and inhibits a data output operation of said datainput/output buffer for an instruction for a data read operation.
 4. Thesemiconductor memory according to claim 2, further including logic meansfor selectively inverting inputs to be output to a path for supplyingaddress information to said detection means in order to detect an accessto a defective memory block designated by the first storage means, andsecond storage means for holding control information for determining thepropriety of the input inverting operation by said logic means.
 5. Amemory device comprising a plurality of semiconductor memories asdefined in claim 3, wherein the semiconductor memories are provided in arelation in which one memory is substituted for a defective memory blockof another, and external terminals having the same function areconnected in common in each semiconductor memory.
 6. A memory cardconstituted by mounting a plurality of memory devices as defined inclaim 5 on a card substrate, whereineach memory device is provided withan external data input/output terminal, a chip selection terminal, andan address input terminal as external terminals, and the chip selectionterminal is connected to chip selection signal wirings different fromeach other on a card substrate in each memory device in which theexternal data input/output terminals are connected to the data wiring ofthe card substrate in common and external address input terminals ofeach memory device are connected to the address signal wiring of thecard substrate in common.
 7. The memory card according to claim 6,further comprising a card controller having one end which is interfacedwith the outside of the card substrate and another end which isconnected to the data wiring, chip selection wiring, and address signalwiring, and the card controller includes decoding means for decodingpart of address information supplied from an external unit to generatethe chip selection signal.
 8. A semiconductor memory comprising:aplurality of memory blocks having a plurality of electrically erasablememory cells; a data input/output buffer for receiving data written inthe memory blocks from an external unit and for outputting data read outof the memory blocks to an external unit; control means for controllingthe rewriting and reading of data for the memory cells; storage meansfor designating some defective memory blocks included in said pluralityof memory blocks; and detection means for detecting the defective memoryblocks designated by said storage means in accordance with an addresssignal; whereinsaid control means inhibits a data rewrite operation foran instruction for a data rewrite operation when said detection meansdetects an access to a defective memory block, generates a status signalrepresenting the completion of a data rewrite operation in such a waythat the status can be output to an external unit, and inhibits a dataoutput operation of said data input/output buffer for an instruction fora data read operation.
 9. A semiconductor memory comprising:a pluralityof memory blocks having a plurality of memory cells; a data input/outputbuffer for receiving data written in the memory blocks from an externalunit and for outputting data read out of the memory blocks to anexternal unit; control means for controlling the rewriting and readingof data for the memory cells; and storage means which designatesdefective memory blocks included in said plurality of memory blocks;whereinsaid control means inhibits a data rewrite operation for aninstruction for a data rewrite operation for defective memory blocksdesignated by said storage means and inhibits a data output operation ofsaid data input/output buffer for an instruction for a data readoperation.
 10. A semiconductor memory comprising:a plurality ofelectrically erasable memory cells forming two memory blocks, one ofwhich is designated by the least significant bit of an address signal; adata input/output buffer for receiving data written in the memory blocksfrom an external unit and for outputting data read out of the memoryblocks to an external unit; control means for controlling the rewritingand reading of data for the memory cells; storage means for designatingone of the two memory blocks; and detection means for detecting anaccess to a defective memory block designated by said storage means inaccordance with the least significant bit of an address signal;whereinsaid control means generates a status signal representing thecompletion of a data rewrite operation for an instruction for a datarewrite operation in such a way that the status can be output to anexternal unit irrespective of the completion of the data rewriteoperation when said detection means detects an access to a defectivememory block and inhibits a data output operation of said datainput/output buffer for an instruction for a data read operation.
 11. Asemiconductor memory comprising:a plurality of electrically erasablememory cells forming two memory blocks, one of which is designated bythe most significant bit of an address signal; a data input/outputbuffer for receiving data written in the memory blocks from an externalunit and for outputting data read out of the memory blocks to anexternal unit; control means for controlling the rewriting and readingof data for the memory cells; storage means for designating one of thetwo memory blocks; and detection means for detecting an access to adefective memory block designated by said storage means in accordancewith the most significant bit of an address signal; whereinsaid controlmeans inhibits a data rewrite operation for an instruction for a datarewrite operation and generates a status signal representing thecompletion of the data rewrite operation when said detection meansdetects an access to a defective memory block and inhibits a data outputoperation of said data input/output buffer for an instruction for a dataread operation.